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Janus Henderson Government Money Market Fund

Ticker: JGVXX Class D Shares*

* Effective July 6, 2020, Class D Shares are open to new investors. Until that time, Class D Shares remain closed to new investors, with certain limited exceptions.

Summary Prospectus dated October 28, 2019
As Supplemented June 19, 2020

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, reports to shareholders, 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.

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 Objectives

Janus Henderson Government Money Market Fund seeks capital preservation and liquidity with current income as a secondary objective.

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(1)	0.20%
Other Expenses	0.39%
Total Annual Fund Operating Expenses	0.59%

(1)  Annual Fund Operating Expenses were restated, effective on or about February 1, 2020, to reflect a reduction to the administration fee paid by the Fund to Janus Capital.

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	$ 60	$ 189	$ 329	$ 738

1  Janus Henderson Government Money Market Fund

Principal investment strategies

The Fund pursues its investment objectives by primarily investing, under normal circumstances, at least 80% of its net assets (plus any borrowings for investment purposes) in U.S. Government securities and repurchase agreements that are collateralized by U.S. Government securities.

The Fund operates as a “government money market fund” as such term is defined in or interpreted under Rule 2a-7 under the Investment Company Act of 1940, as amended. As a government money market fund, the Fund pursues its investment objectives by normally investing at least 99.5% of its total assets in cash, U.S. Government securities, and/or repurchase agreements that are collateralized fully (i.e., collateralized by cash and/or government securities). The Fund’s investments in U.S. Government securities may include obligations issued and/or guaranteed as to principal and interest by the United States Government or by its agencies and instrumentalities, and repurchase agreements secured by such obligations. Although U.S. Government agencies and instrumentalities may be chartered or sponsored by Acts of Congress, their securities are not issued by, and may not be guaranteed by (i.e., backed by the full faith and credit of), the U.S. Treasury. Some government agency and instrumentality securities not backed by the full faith and credit of the United States are supported by the issuer’s ability to borrow from the U.S. Treasury, some are supported only by the credit of the issuer, and some are supported by the United States in some other way. The Fund’s investments in securities issued by U.S. Government agencies and instrumentalities may be significant.

The Fund will:

• invest in high-quality, short-term money market instruments that present minimal credit risks, as determined by Janus Capital

• invest only in U.S. dollar-denominated instruments that have a remaining maturity of 397 days or less (as calculated pursuant to Rule 2a-7 under the Investment Company Act of 1940, as amended)

• maintain a dollar-weighted average portfolio maturity of 60 days or less and maintain a dollar-weighted average portfolio life (portfolio maturity measured without reference to any maturity shortening provisions of adjustable rate securities by reference to their interest rate reset dates) of 120 days or less

As a government money market fund, the Board of Trustees has determined not to subject the Fund to a liquidity fee and/or redemption gate on Fund redemptions. Please note that the Board of Trustees has reserved the ability to change this determination with respect to liquidity fees and/or redemption gates, but only after providing appropriate prior notice to shareholders.

Principal investment risks

Money Market Risk.  You could lose money by investing in the Fund. Although the Fund seeks to preserve the value of your investment at $1.00 per share, it cannot guarantee it will do so. An investment in the Fund is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency. Factors such as, but not limited to, an increase in interest rates, a decline in the credit quality of one or more issuers, large redemptions of the Fund’s Shares, or adverse market conditions impacting the trading or the value of money market instruments could cause the Fund’s share price to decrease below $1.00. Janus Capital has no legal obligation to provide financial support to the Fund, and you should not expect that Janus Capital will provide financial support to the Fund at any time. Accordingly, if the value of Fund Shares were to fall below $1.00 per share, there is no guarantee that Janus Capital or its affiliates would protect the Fund or redeeming shareholders against any loss of principal.

Interest Rate Risk.  Although the Fund seeks to invest only in high-quality, short-term money market instruments, there is a risk that the value of the securities it holds will fall as a result of the changes in interest rates, which are near historically low levels. Rising interest rates could cause the value of the Fund’s investments to decline, and a decline in interest rates is likely to cause the Fund’s yield to decline. During periods of unusually low interest rates, the Fund’s yield may approach zero. Such low interest rate environments may prevent the Fund from providing a positive yield or could impair the Fund’s ability to maintain the value of your investment at $1.00 per share. Over time, the real value of the Fund’s yield may be eroded by inflation.

Credit Quality Risk.  The value of the securities which the Fund holds may fall based on an issuer’s actual or perceived creditworthiness, or an issuer’s ability to meet its obligations (potentially even the U.S. Government). The credit quality of the

2  Janus Investment Fund

Fund’s holdings can change rapidly in certain market environments and any downgrade or default of a portfolio security could cause the Fund’s yield to fall or cause the value of the Fund’s Shares to fall below $1.00 per share.

Liquidity Risk.  The liquidity of the securities which the Fund holds may deteriorate rapidly due to credit events affecting one or more issuers or guarantors or due to general market conditions and a lack of willing buyers. In such cases, the Fund may have to accept a lower price or may be unable to sell a security. An inability to sell one or more securities may negatively affect the Fund’s ability to maintain a $1.00 share price or prevent the Fund from being able to take advantage of other investment opportunities. Additionally, adverse market conditions impacting the trading of the value of money market instruments and/or an unusually high volume of redemption requests could cause the Fund to be unable to pay redemption proceeds within a short period of time. If the Fund is forced to sell securities at an unfavorable time and/or under unfavorable conditions, such sales may adversely affect the Fund’s ability to maintain the value of your investment at $1.00 per share.

Market Risk.  The Fund’s yield will vary as the short-term securities in its portfolio mature and the proceeds are reinvested in securities with different interest rates. For capital preservation and liquidity, the Fund may have a greater concentration in short-term securities including, but not limited to, investing up to all of its assets in overnight securities, which may result in a reduction of the Fund’s yield.

Collateral Risk.  With respect to collateral received in repurchase transactions or other investments, the Fund may have significant exposure to government agencies not secured by the full faith and credit of the United States. Such exposure, depending on market conditions, could have a negative impact on the Fund, including minimizing the value of any collateral.

Counterparty Risk.  Fund transactions involving a counterparty are subject to the risk that the counterparty or a third party will not fulfill its obligation to the Fund (“counterparty risk”). Counterparty risk may arise because of the counterparty’s financial condition (i.e., financial difficulties, bankruptcy, or insolvency), market activities and developments, or other reasons, whether foreseen or not. A counterparty’s inability to fulfill its obligation may result in significant financial loss to the Fund. The Fund may be unable to recover its investment from the counterparty or may obtain a limited recovery, and/or recovery may be delayed. The Fund may be exposed to counterparty risk through its investments in certain securities, including, but not limited to, repurchase agreements and debt securities. The Fund intends to enter into financial transactions with counterparties that Janus Capital believes to be creditworthy at the time of the transaction. There is always the risk that Janus Capital’s analysis of a counterparty’s creditworthiness is incorrect or may change due to market conditions. To the extent that the Fund focuses its transactions with a limited number of counterparties, it will have greater exposure to the risks associated with one or more counterparties.

Variable and Floating Rate Demand Notes Risk.  Variable and floating rate securities are subject to changes in value based on changes in market interest rates or changes in the issuer’s or guarantor’s creditworthiness. In addition, the absence of an active market for these securities could make it difficult for the Fund to dispose of them if the issuer defaults.

U.S. Government Securities Risk.  Certain U.S. Government securities are not guaranteed or backed by the full faith and credit of the United States. For these securities, the Fund must look principally to the agency or instrumentality issuing or guaranteeing the securities for repayment and may not be able to assert a claim against the United States if the agency or instrumentality does not meet its commitment. Such securities may involve increased risk of loss of principal and interest compared to government debt securities that are backed by the full faith and credit of the United States.

Repurchase Agreement Risk.  Repurchase agreements involve the risk that the seller will fail to repurchase the security, as agreed. In that case, the Fund will bear the risk of market value fluctuations until the security can be sold and may encounter delays and incur costs in liquidating the security.

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 February 16, 2010, as a result of the restructuring of Class J Shares, the predecessor share class. The performance shown for Class D Shares for periods prior to February 16, 2010, reflects the performance of the Fund’s former Class J Shares, calculated using the fees and expenses in effect during the periods shown, net of any applicable fee and expense limitations or waivers. If Class D Shares of the Fund had been available during periods prior to February 16, 2010, the performance shown may have been different. The

3  Janus Henderson Government Money Market Fund

performance shown for the 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 shows how the Fund’s returns over different periods average out. 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 does not necessarily indicate how it will perform in the future.Updated performance information is available at janushenderson.com/allfunds or by calling 1-800-525-3713.

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

Best Quarter: 4th Quarter 2018 0.43% Worst Quarter: 4th Quarter 2014 0.00%

The Fund’s year-to-date return as of the calendar quarter ended September 30, 2019 was 1.33%.

Average Annual Total Returns (periods ended 12/31/18)
	1 Year	5 Years	10 Years	Since Inception (2/14/95)
Class D Shares
Return Before Taxes	1.31%	0.33%	0.17%	2.17%

The 7-day yield on December 31, 2018 was 1.81% for Janus Henderson Government Money Market Fund.

Management

Investment Adviser:  Janus Capital Management LLC

Portfolio Managers: David Spilsted is Executive Vice President and Co-Portfolio Manager of the Fund, which he has co-managed since July 2017.Garrett Strum is Executive Vice President and Co-Portfolio Manager of the Fund, which he has managed or co-managed since May 2017.

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

4  Janus Investment Fund

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

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

With respect to share classes not offered in this Prospectus, the Fund and its related companies 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 Government Money Market Fund