497K

[JANUS HENDERSON LOGO]

Janus Henderson Forty Fund

Ticker:	JDCAX	Class A Shares	JARTX	Class S Shares	JFRNX	Class N Shares	JACTX	Class T Shares
	JACCX	Class C Shares	JCAPX	Class I Shares	JDCRX	Class R Shares

Summary Prospectus dated January 28, 2019

Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. You can find the Fund’s Prospectus and other information about the Fund online at janushenderson.com/info. You can also get this information at no cost by calling a Janus Henderson representative at 1-877-335-2687 or by sending an email request to prospectusrequest@janushenderson.com.

Beginning on January 1, 2021, as permitted by regulations adopted by the Securities and Exchange Commission, paper copies of the Fund’s shareholder reports will no longer be sent by mail, unless you specifically request paper copies of the reports from the Fund or your plan sponsor, broker-dealer, or financial intermediary, or if you invest directly with the Fund, by contacting a Janus Henderson representative. Instead, the reports will be made available on a website, and you will be notified by mail each time a report is posted and provided with a website link to access the report.

If you already elected to receive shareholder reports electronically, you will not be affected by this change and you need not take any action. You may elect to receive shareholder reports and other communications from the Fund electronically by contacting your plan sponsor, broker-dealer, or financial intermediary, or if you invest directly with the Fund, by visiting janushenderson.com/edelivery.

You may elect to receive all future reports in paper free of charge. If you do not invest directly with the Fund, you should contact your plan sponsor, broker-dealer, or financial intermediary, to request to continue receiving paper copies of your shareholder reports. If you invest directly with the Fund, you can call 1-800-525-3713 to let the Fund know that you wish to continue receiving paper copies of your shareholder reports. Your election to receive reports in paper will apply to all Janus Henderson mutual funds where held (i.e., all Janus Henderson mutual funds held in your account if you invest through your financial intermediary or all Janus Henderson mutual funds held with the fund complex if you invest directly with a fund).

INVESTMENT OBJECTIVE

Janus Henderson Forty Fund seeks long-term growth of capital.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund. Each share class has different expenses, but represents an investment in the same Fund. For Class A Shares, you may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $50,000 in the Fund or in other Janus Henderson mutual funds. More information about these and other discounts, as well as eligibility requirements for each share class, is available from your financial professional and in the “Purchases” section on page 100 of the Fund’s Prospectus and in the “Purchases” section on page 85 of the Fund’s Statement of Additional Information. In addition, please see Appendix A – Intermediary Sales Charge Waivers and Discounts. You may also incur brokerage commissions charged by your broker or financial intermediary when buying Class I Shares or Class N Shares of the Fund that are not reflected in the table or in the example below.

SHAREHOLDER FEES
(fees paid directly from your investment)

Class A

Class C

Class S

Class I

Class N

Class R

Class T

Maximum Sales Charge (load) Imposed on Purchases (as a percentage of offering price)

5.75%

None

Maximum Deferred Sales Charge (load) (as a percentage of the lower of original purchase price or redemption proceeds)

None

1.00%

None

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)	Class A	Class C	Class S	Class I	Class N	Class R	Class T
Management Fees (may adjust up or down)	0.64%	0.64%	0.64%	0.64%	0.64%	0.64%	0.64%
Distribution/Service (12b-1) Fees	0.25%	1.00%	0.25%	None	None	0.50%	None
Other Expenses	0.15%	0.10%	0.26%	0.08%	0.02%	0.26%	0.27%
Total Annual Fund Operating Expenses	1.04%	1.74%	1.15%	0.72%	0.66%	1.40%	0.91%

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EXAMPLE:

The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and reinvest all dividends and distributions. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

If Shares are redeemed:	1 Year	3 Years	5 Years	10 Years
Class A Shares	$ 675	$ 887	$ 1,116	$ 1,773
Class C Shares	$ 277	$ 548	$ 944	$ 2,052
Class S Shares	$ 117	$ 365	$ 633	$ 1,398
Class I Shares	$ 74	$ 230	$ 401	$ 894
Class N Shares	$ 67	$ 211	$ 368	$ 822
Class R Shares	$ 143	$ 443	$ 766	$ 1,680
Class T Shares	$ 93	$ 290	$ 504	$ 1,120

If Shares are not redeemed:	1 Year	3 Years	5 Years	10 Years
Class A Shares	$ 675	$ 887	$ 1,116	$ 1,773
Class C Shares	$ 177	$ 548	$ 944	$ 2,052
Class S Shares	$ 117	$ 365	$ 633	$ 1,398
Class I Shares	$ 74	$ 230	$ 401	$ 894
Class N Shares	$ 67	$ 211	$ 368	$ 822
Class R Shares	$ 143	$ 443	$ 766	$ 1,680
Class T Shares	$ 93	$ 290	$ 504	$ 1,120

Portfolio Turnover: The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover rate may indicate higher transaction costs and may result in higher taxes when Fund shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the Example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 37% of the average value of its portfolio.

PRINCIPAL INVESTMENT STRATEGIES

The Fund pursues its investment objective by normally investing primarily in a core group of 20-40 common stocks selected for their growth potential. The Fund may invest in companies of any size, from larger, well-established companies to smaller, emerging growth companies. The Fund may also invest in foreign securities, which may include investments in emerging markets. As of September 30, 2018, the Fund held stocks of 41 companies. Of these holdings, 20 comprised approximately 69.82% of the Fund’s holdings.

The portfolio managers apply a “bottom up” approach in choosing investments. In other words, the portfolio managers look at companies one at a time to determine if a company is an attractive investment opportunity and if it is consistent with the Fund’s investment policies.

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to one-third of its total assets as determined at the time of the loan origination.

PRINCIPAL INVESTMENT RISKS

The biggest risk is that the Fund’s returns will vary, and you could lose money. The Fund is designed for long-term investors seeking an equity portfolio, including common stocks. Common stocks tend to be more volatile than many other investment choices.

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also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money. Market risk may affect a single issuer, industry, economic sector, or the market as a whole.

Growth Securities Risk. The Fund invests in companies that the portfolio managers believe have growth potential. Securities of companies perceived to be “growth” companies may be more volatile than other stocks and may involve special risks. If the portfolio managers’ perception of a company’s growth potential is not realized, the securities purchased may not perform as expected, reducing the Fund’s returns. In addition, because different types of stocks tend to shift in and out of favor depending on market and economic conditions, “growth” stocks may perform differently from the market as a whole and other types of securities.

Nondiversification Risk. The Fund is classified as nondiversified under the Investment Company Act of 1940, as amended. This gives the Fund’s portfolio managers more flexibility to hold larger positions in a smaller number of securities. As a result, an increase or decrease in the value of a single security held by the Fund may have a greater impact on the Fund’s net asset value and total return.

Mid-Sized Companies Risk. The Fund’s investments in securities issued by mid-sized companies may involve greater risks than are customarily associated with larger, more established companies. Securities issued by mid-sized companies tend to be more volatile than securities issued by larger or more established companies and may underperform as compared to the securities of larger or more established companies.

Foreign Exposure Risk. The Fund may have exposure to foreign markets as a result of its investments in foreign securities, including investments in emerging markets, which can be more volatile than the U.S. markets. As a result, its returns and net asset value may be affected to a large degree by fluctuations in currency exchange rates or political or economic conditions in a particular country. In some foreign markets, there may not be protection against failure by other parties to complete transactions. It may not be possible for the Fund to repatriate capital, dividends, interest, and other income from a particular country or governmental entity. In addition, a market swing in one or more countries or regions where the Fund has invested a significant amount of its assets may have a greater effect on the Fund’s performance than it would in a more geographically diversified portfolio. The Fund’s investments in emerging market countries may involve risks greater than, or in addition to, the risks of investing in more developed countries.

Securities Lending Risk. The Fund may seek to earn additional income through lending its securities to certain qualified broker-dealers and institutions. There is the risk that when portfolio securities are lent, the securities may not be returned on a timely basis, and the Fund may experience delays and costs in recovering the security or gaining access to the collateral provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

Management Risk. The Fund is an actively managed investment portfolio and is therefore subject to the risk that the investment strategies employed for the Fund may fail to produce the intended results. The Fund may underperform its benchmark index or other mutual funds with similar investment objectives.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance Information

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class S Shares, Class A Shares, Class C Shares, Class I Shares, and Class R Shares of the Fund commenced operations on July 6, 2009, after the reorganization of each corresponding class of shares of Janus Adviser Forty Fund (the “JAD predecessor fund”) into each respective share class of the Fund. Class T Shares of the Fund commenced operations on July 6, 2009. Class N Shares of the Fund commenced operations on May 31, 2012.

•

The performance shown for Class S Shares reflects the performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) from August 1, 2000 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods prior to August 1, 2000, the performance shown for Class S Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement

3	Janus Henderson Forty Fund

	Shares into the JAD predecessor fund). The performance shown for certain periods prior to August 1, 2000 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.
•	The performance shown for Class A Shares reflects the performance of the JAD predecessor fund’s Class A Shares from September 30, 2004 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class A Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to September 30, 2004, the performance shown for Class A Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class A Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to September 30, 2004 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.
•	The performance shown for Class C Shares reflects the performance of the JAD predecessor fund’s Class C Shares from September 30, 2002 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class C Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to September 30, 2002, the performance shown for Class C Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class C Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to September 30, 2002 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.
•	The performance shown for Class I Shares reflects the performance of the JAD predecessor fund’s Class I Shares from November 28, 2005 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class I Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to November 28, 2005, the performance shown for Class I Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class I Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to November 28, 2005 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.
•	The performance shown for Class N Shares reflects the performance of the Fund’s Class S Shares from July 6, 2009 to May 31, 2012, calculated using the fees and expenses of Class S Shares, net of any applicable fee and expense limitations or waivers. For the period from August 1, 2000 to July 6, 2009, the performance shown for Class N Shares reflects the performance of Class S Shares (formerly named Class I Shares) of the JAD predecessor fund (prior to the reorganization of those Class S Shares into the Fund), calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods prior to August 1, 2000, the performance shown for Class N Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance for certain periods prior to August 1, 2000 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.
•	The performance shown for Class R Shares reflects the performance of the JAD predecessor fund’s Class R Shares from September 30, 2004 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class R Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods August 1, 2000 to September 30, 2004, the performance shown for Class R Shares reflects the historical performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares). For the periods prior to August 1, 2000, the performance shown for Class R Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to September 30, 2004 was calculated using the fees and expenses of Class R Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.
•	The performance shown for Class T Shares reflects the performance of the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) from August 1, 2000 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods prior to August 1, 2000, the performance shown for Class T Shares reflects the historical performance of the

4	Janus Investment Fund

Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to August 1, 2000 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

If Class A Shares, Class C Shares, Class I Shares, Class R Shares, and Class T Shares of the Fund had been available during each period prior to July 6, 2009, or Class N Shares of the Fund had been available during periods prior to May 31, 2012, the performance shown for each respective share class may have been different. The performance shown for the periods following the Fund’s commencement of Class S Shares, Class A Shares, Class C Shares, Class I Shares, Class N Shares, Class R Shares, and Class T Shares reflects the fees and expenses of each respective share class, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The bar chart figures do not include any applicable sales charges that an investor may pay when they buy or sell Class A Shares or Class C Shares of the Fund. If sales charges were included, the returns would be lower. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

The Fund’s past performance (before and after taxes) does not necessarily indicate how it will perform in the future. Updated performance information is available at janushenderson.com/performance or by calling 1-877-335-2687.

Annual Total Returns for Class S Shares (calendar year-end)

Best Quarter: 2nd Quarter 2009 20.90%

Worst Quarter: 3rd Quarter 2011 – 15.55%

Average Annual Total Returns (periods ended 12/31/18)
	1 Year	5 Years	10 Years	Since Inception of Predecessor Fund (5/1/97)
Class S Shares
Return Before Taxes	1.04%	10.04%	13.95%	10.66%
Return After Taxes on Distributions	– 0.92%	6.03%	11.33%	9.39%
Return After Taxes on Distributions and Sale of Fund Shares⁽¹⁾	2.04%	7.20%	11.18%	9.11%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%

5	Janus Henderson Forty Fund

Average Annual Total Returns (periods ended 12/31/18)
	1 Year	5 Years	10 Years	Since Inception of Predecessor Fund (5/1/97)
Class A Shares
Return Before Taxes⁽²⁾	– 4.63%	8.82%	13.41%	10.48%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%
Class C Shares
Return Before Taxes⁽³⁾	– 0.39%	9.46%	13.30%	10.09%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%
Class I Shares
Return Before Taxes	1.50%	10.47%	14.41%	10.66%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%
Class N Shares
Return Before Taxes	1.59%	10.56%	13.95%	10.66%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%
Class R Shares
Return Before Taxes	0.80%	9.73%	13.64%	10.40%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%
Class T Shares
Return Before Taxes	1.32%	10.30%	13.95%	10.66%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%

(1)	If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund’s other return figures.
(2)	Calculated assuming maximum permitted sales loads.
(3)	The one year return is calculated to include the contingent deferred sales charge.

The Fund’s primary benchmark index is the Russell 1000^® Growth Index. The Fund also compares its performance to the S&P 500^® Index. The Russell 1000^® Growth Index is used to calculate the Fund’s performance fee adjustment. The indices are described below.

•	The Russell 1000^® Growth Index measures the performance of those Russell 1000^® companies with higher price-to-book ratios and higher forecasted growth values.

6	Janus Investment Fund

•	The S&P 500^® Index is a commonly recognized, market-capitalization weighted index of 500 widely held equity securities, designed to measure broad U.S. equity performance.

After-tax returns are calculated using distributions for the Fund’s Class S Shares for periods following July 6, 2009; for the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) for the periods August 1, 2000 to July 6, 2009; and actual distributions for other classes of shares for periods prior to August 1, 2000. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-advantaged account, such as a 401(k) plan or an IRA.

After-tax returns are only shown for Class S Shares of the Fund. After-tax returns for the other classes of Shares will vary from those shown for Class S Shares due to varying sales charges (as applicable), fees, and expenses among the classes.

MANAGEMENT

Investment Adviser: Janus Capital Management LLC

Portfolio Managers: A. Douglas Rao is Executive Vice President and Co-Portfolio Manager of the Fund, which he has managed or co-managed since June 2013. Nick Schommer, CFA, is Executive Vice President and Co-Portfolio Manager of the Fund, which he has co-managed since January 2016.

PURCHASE AND SALE OF FUND SHARES

Minimum Investment Requirements*

Class A Shares, Class C Shares**, Class S Shares, Class R Shares, and Class T Shares
Non-retirement accounts	$ 2,500***
Certain tax-advantaged accounts or UGMA/UTMA accounts	$ 500
Class I Shares
Through an intermediary institution
• non-retirement accounts	$ 2,500
• certain tax-advantaged accounts or UGMA/UTMA accounts	$ 500
Class N Shares
Retirement investors (investing through an adviser-assisted, employer-sponsored retirement plan)	None
Retail investors (investing through a financial intermediary omnibus account)	$2,500****
Institutional investors (investing directly with the Fund)	$ 1,000,000

*	Exceptions to these minimums may apply for certain tax-advantaged, tax-qualified and retirement plans, accounts held through certain wrap programs, and certain retail brokerage accounts.
**	The maximum purchase in Class C Shares is $500,000 for any single purchase.
***	Shareholders who invest through financial intermediaries with supermarket and/or self-directed brokerage platforms that maintain omnibus accounts and charge asset-based service fees may not be subject to this minimum. Please contact your financial intermediary for more information.
****	Investors in certain tax-advantaged accounts or accounts held through certain wrap programs may not be subject to this minimum.

Purchases, exchanges, and redemptions can generally be made only through institutional channels, such as financial intermediaries and retirement platforms. Class I Shares may be purchased directly by certain institutional investors who established Class I Shares accounts before August 4, 2017. You should contact your financial intermediary or refer to your plan documents for information on how to invest in the Fund. Requests must be received in good order by the Fund or its agents (financial intermediary or plan sponsor, if applicable) prior to the close of the regular trading session of the New York Stock Exchange in order to receive that day’s net asset value. For additional information, refer to “Purchases,” “Exchanges,” and/or “Redemptions” in the Prospectus.

7	Janus Henderson Forty Fund

Tax Information

The Fund’s distributions are taxable, and will be taxed as ordinary income or capital gains, unless you are investing through a tax-advantaged arrangement, such as a 401(k) plan or an individual retirement account (in which case you may be taxed upon withdrawal of your investment from such account).

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase Class A Shares, Class C Shares, Class S Shares, Class I Shares, Class R Shares, or Class T Shares of the Fund through a broker-dealer or other financial intermediary (such as a bank), the Fund and its related companies may pay the intermediary for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing the broker-dealer or other intermediary and your salesperson to recommend the Fund over another investment or to recommend one share class over another. There is some regulatory uncertainty concerning whether marketing support or other similar payments may be made or received in connection with Class I Shares where a financial intermediary has imposed its own sales charges or transaction fees. As a result, based on future regulatory developments, such payments may be terminated, or the Fund may prohibit financial intermediaries from imposing such sales charges or transaction fees in connection with Class I Shares. Ask your salesperson or visit your financial intermediary’s website for more information.

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[JANUS HENDERSON LOGO]

Janus Henderson Forty Fund

Ticker:

JFRDX

Class D Shares*

* Class D Shares are closed to certain new investors.

Summary Prospectus dated January 28, 2019

Before you invest, you may want to review the Fund’s Prospectus, which contains more information about the Fund and its risks. You can find the Fund’s Prospectus and other information about the Fund online at janushenderson.com/reports. You can also get this information at no cost by calling a Janus Henderson representative at 1-800-525-3713 or by sending an email request to prospectusorder@janushenderson.com.

INVESTMENT OBJECTIVE

Janus Henderson Forty Fund seeks long-term growth of capital.

FEES AND EXPENSES OF THE FUND

This table describes the fees and expenses that you may pay if you buy and hold Shares of the Fund.

ANNUAL FUND OPERATING EXPENSES (expenses that you pay each year as a percentage of the value of your investment)		Class D
Management Fees (may adjust up or down)		0.64%
Other Expenses		0.15%
Total Annual Fund Operating Expenses		0.79%

EXAMPLE:

The Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated, reinvest all dividends and distributions, and then redeem all of your Shares at the end of each period. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

	1 Year	3 Years	5 Years	10 Years
Class D Shares	$ 81	$ 252	$ 439	$ 978

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PRINCIPAL INVESTMENT STRATEGIES

The Fund may lend portfolio securities on a short-term or long-term basis, in an amount equal to up to one-third of its total assets as determined at the time of the loan origination.

PRINCIPAL INVESTMENT RISKS

Market Risk. The value of the Fund’s portfolio may decrease if the value of an individual company or security, or multiple companies or securities, in the portfolio decreases or if the portfolio managers’ belief about a company’s intrinsic worth is incorrect. Further, regardless of how well individual companies or securities perform, the value of the Fund’s portfolio could also decrease if there are deteriorating economic or market conditions. It is important to understand that the value of your investment may fall, sometimes sharply, in response to changes in the market, and you could lose money. Market risk may affect a single issuer, industry, economic sector, or the market as a whole.

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provided to the Fund to collateralize the loan. If the Fund is unable to recover a security on loan, the Fund may use the collateral to purchase replacement securities in the market. There is a risk that the value of the collateral could decrease below the cost of the replacement security by the time the replacement investment is made, resulting in a loss to the Fund.

An investment in the Fund is not a bank deposit and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

Performance Information

The following information provides some indication of the risks of investing in the Fund by showing how the Fund’s performance has varied over time. Class D Shares of the Fund commenced operations on January 27, 2017. The performance shown for Class D Shares reflects the performance of the Fund’s Class S Shares from July 6, 2009 to January 27, 2017, calculated using the fees and expenses of Class S Shares, net of any applicable fee and expense limitations or waivers. The performance shown for Class D Shares reflects the performance of Janus Adviser Forty Fund’s (the “JAD predecessor fund”) Class S Shares (formerly named Class I Shares) from August 1, 2000 to July 6, 2009 (prior to the reorganization), calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, net of any applicable fee and expense limitations or waivers. For the periods prior to August 1, 2000, the performance shown for Class D Shares reflects the historical performance of the Retirement Shares of Janus Aspen Series – Forty Portfolio (as a result of a separate prior reorganization of those Retirement Shares into the JAD predecessor fund). The performance shown for certain periods prior to August 1, 2000 was calculated using the fees and expenses of Class S Shares of the JAD predecessor fund, without the effect of any fee and expense limitations or waivers.

If Class D Shares of the Fund had been available during periods prior to January 27, 2017, the performance shown may have been different. The performance shown for periods following the Fund’s commencement of Class D Shares reflects the fees and expenses of Class D Shares, net of any applicable fee and expense limitations or waivers.

The bar chart depicts the change in performance from year to year during the periods indicated. The table compares the Fund’s average annual returns for the periods indicated to broad-based securities market indices. All figures assume reinvestment of dividends and distributions. For certain periods, the Fund’s performance reflects the effect of expense waivers. Without the effect of these expense waivers, the performance shown would have been lower.

Annual Total Returns for Class D Shares (calendar year-end)

Best Quarter: 2nd Quarter 2009 20.90%

Worst Quarter: 3rd Quarter 2011 – 15.55%

3	Janus Henderson Forty Fund

Average Annual Total Returns (periods ended 12/31/18)
	1 Year	5 Years	10 Years	Since Inception of Predecessor Fund (5/1/97)
Class D Shares
Return Before Taxes	1.43%	10.04%	13.95%	10.66%
Return After Taxes on Distributions	– 0.52%	6.03%	11.33%	9.39%
Return After Taxes on Distributions and Sale of Fund Shares⁽¹⁾	2.27%	7.20%	11.18%	9.11%
Russell 1000^® Growth Index (reflects no deduction for expenses, fees, or taxes)	– 1.51%	10.40%	15.29%	7.22%
S&P 500^® Index (reflects no deduction for expenses, fees, or taxes)	– 4.38%	8.49%	13.12%	7.42%

(1)	If the Fund incurs a loss, which generates a tax benefit, the Return After Taxes on Distributions and Sale of Fund Shares may exceed the Fund’s other return figures.

•	The Russell 1000^® Growth Index measures the performance of those Russell 1000^® companies with higher price-to-book ratios and higher forecasted growth values.
•	The S&P 500^® Index is a commonly recognized, market-capitalization weighted index of 500 widely held equity securities, designed to measure broad U.S. equity performance.

After-tax returns are calculated using distributions for the Fund’s Class D Shares for the periods following January 27, 2017; for the Fund’s Class S Shares for periods January 27, 2017 to July 6, 2009; for the JAD predecessor fund’s Class S Shares (formerly named Class I Shares) for the periods August 1, 2000 to July 6, 2009; and actual distributions for other classes of shares for periods prior to August 1, 2000. If Class D Shares of the Fund had been available during these earlier periods, distributions may have been different and thus, after-tax returns may have been different from those shown. After-tax returns are calculated using the historically highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on your individual tax situation and may differ from those shown in the preceding table. The after-tax return information shown above does not apply to Fund shares held through a tax-advantaged account, such as a 401(k) plan or an IRA.

4	Janus Investment Fund

MANAGEMENT

Investment Adviser: Janus Capital Management LLC

PURCHASE AND SALE OF FUND SHARES

Minimum Investment Requirements
To open a new regular Fund account	$2,500
To open a new regular Fund account with an automatic investment program of $50 per month	$ 100
To open a new UGMA/UTMA account, Coverdell Education Savings Account, or a retirement Fund account
• without an automatic investment program	$1,000
• with an automatic investment program of $50 per month	$ 100
To add to any existing type of Fund account without an automatic investment program	$ 50

You may generally purchase, exchange, or redeem Fund Shares on any business day by written request, wire transfer, telephone, and in most cases, online at janushenderson.com/individual. You may conduct transactions by mail (Janus Henderson, P.O. Box 219109, Kansas City, MO 64121-9109), or by telephone at 1-800-525-3713. Purchase, exchange, or redemption requests must be received in good order by the Fund or its agents prior to the close of the regular trading session of the New York Stock Exchange in order to receive that day’s net asset value. For additional information, refer to “To Open an Account or Buy Shares,” “To Exchange Shares,” and/or “To Sell Shares” in the Prospectus.

Tax Information

Payments to Broker-Dealers and Other Financial Intermediaries

With respect to certain other classes of shares, the Fund and its related companies may pay select broker-dealer firms or other financial intermediaries for the sale of Fund shares and related services. These payments may create a conflict of interest by influencing a broker-dealer or other intermediary or a salesperson to recommend the Fund over another investment or to recommend one share class over another.

5	Janus Henderson Forty Fund