SAM (STRATEGIC ASSET MANAGEMENT) FLEXIBLE INCOME PORTFOLIO

Class	A	C	J	P	Inst.	R-1	R-2	R-3	R-4	R-5
Ticker Symbol(s)	SAUPX	SCUPX	PFIJX	PFITX	PIFIX	PFIGX	PFIVX	PFIPX	PFILX	PFIFX

Principal Funds, Inc. Summary Prospectus March 1, 2017 as amended March 24, 2017

On March 13, 2017, the Board of Directors of Principal Funds, Inc. (“PFI”) approved the automatic conversion of Class P shares into Institutional Class shares. After June 22, 2017, Class P shares will no longer be available for purchase. Following the close of business on June 23, 2017, Class P shares will automatically convert into Institutional Class shares of the same Fund on the basis of the share classes’ relative net asset values on such date without the imposition of a sales charge or any other charge. At such time, delete references to Class P from this Prospectus.

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 www.principalfunds.com/prospectuses. You can also get this information at no cost by calling 1-800-222-5852 or by sending an email to prospectus@principalfunds.com.

This Summary prospectus incorporates by reference the Statutory Prospectus dated March 1, 2017 as supplemented March 17, 2017 and March 24, 2017, and the Statement of Additional Information dated March 1, 2017 as supplemented March 17, 2017 and March 24, 2017 (which may be obtained in the same manner as the Prospectus).

Objective: The Portfolio seeks to provide a high level of total return (consisting of reinvestment of income with some capital appreciation).

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. You may qualify for sales charge discounts if you and your family invest, or agree to invest in the future, at least $100,000 in Class A Shares of Principal Funds, Inc. More information about these and other discounts is available from your financial professional and in “Choosing a Share Class and The Costs of Investing” beginning on page 417 of the Fund’s prospectus and “Multiple Class Structure” beginning on page 6 of the Fund’s Statement of Additional Information.

Shareholder Fees (fees paid directly from your investment)

	Share Class
	A	C	J	P	Inst.	R-1	R-2	R-3	R-4	R-5
Maximum Sales Charge (Load) Imposed on Purchases (as a percentage of offering price)	3.75%	None	None	None	None	None	None	None	None	None
Maximum Deferred Sales Charge (Load) (as a percentage of the offering price or NAV when Sales Load is paid, whichever is less)	1.00%	1.00%	1.00%	None	None	None	None	None	None	None

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Annual Fund Operating Expenses

(expenses that you pay each year as a percentage of the value of your investment)

	Share Class
	A	C	J	P	Inst.	R-1	R-2	R-3	R-4	R-5
Management Fees (1)	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%
Distribution and/or Service (12b-1) Fees (1)	0.25%	1.00%	0.15%	N/A	N/A	0.35%	0.30%	0.25%	0.10%	N/A
Other Expenses (1)	0.08%	0.10%	0.06%	0.24%	0.01%	0.53%	0.45%	0.32%	0.28%	0.26%
Acquired Fund Fees and Expenses	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%
Total Annual Fund Operating Expenses	1.18%	1.95%	1.06%	1.09%	0.86%	1.73%	1.60%	1.42%	1.23%	1.11%
Expense Reimbursement (2)	N/A	N/A	N/A	(0.04)%	N/A	N/A	N/A	N/A	N/A	N/A
Total Annual Fund Operating Expenses after Expense Reimbursement	1.18%	1.95%	1.06%	1.05%	0.86%	1.73%	1.60%	1.42%	1.23%	1.11%
(1)    Expense information in the table has been restated to reflect current fees.
(2)    Principal Management Corporation ("PMC"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain "Other Expenses" (expressed as a percent of average net assets on an annualized basis) not to exceed 0.20% for Class P shares. It is expected that the expense limit will continue through the period ending February 28, 2018; however, Principal Funds, Inc. and PMC, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

Effective June 23, 2017, delete the Annual Fund Operating Expenses table and footnotes and replace with the following:

Annual Fund Operating Expenses

(expenses that you pay each year as a percentage of the value of your investment)

	Share Class
	A	C	J	Inst.	R-1	R-2	R-3	R-4	R-5
Management Fees (1)	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%	0.28%
Distribution and/or Service (12b-1) Fees (1)	0.25%	1.00%	0.15%	N/A	0.35%	0.30%	0.25%	0.10%	N/A
Other Expenses (1)	0.08%	0.10%	0.06%	0.01%	0.53%	0.45%	0.32%	0.28%	0.26%
Acquired Fund Fees and Expenses	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%	0.57%
Total Annual Fund Operating Expenses	1.18%	1.95%	1.06%	0.86%	1.73%	1.60%	1.42%	1.23%	1.11%
Expense Reimbursement (2)	N/A	N/A	N/A	—%	N/A	N/A	N/A	N/A	N/A
Total Annual Fund Operating Expenses after Expense Reimbursement	1.18%	1.95%	1.06%	0.86%	1.73%	1.60%	1.42%	1.23%	1.11%
(1)    Expense information in the table has been restated to reflect current fees.
(2)    Principal Management Corporation ("PMC"), the investment advisor, has contractually agreed to limit the Fund’s expenses by paying, if necessary, expenses normally payable by the Fund, (excluding interest expense, expenses related to fund investments, acquired fund fees and expenses, and other extraordinary expenses) to maintain a total level of operating expenses (expressed as a percent of average net assets on an annualized basis) not to exceed 0.29% for Institutional Class shares. The expense cap has been added to limit the potential increase in "Other Expenses" that otherwise may occur due to an expected decrease in the number of Institutional Class shareholders of the Fund. It is expected that the expense limit will continue through the period ending June 30, 2018; however, Principal Funds, Inc. and PMC, the parties to the agreement, may mutually agree to terminate the expense limit prior to the end of the period.

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Example

This 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 then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. 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 A	$491	$736	$1,000	$1,753
Class C	298	612	1,052	2,275
Class J	208	337	585	1,294
Class P	107	343	597	1,325
Institutional Class	88	274	477	1,061
Class R-1	176	545	939	2,041
Class R-2	163	505	871	1,900
Class R-3	145	449	776	1,702
Class R-4	125	390	676	1,489
Class R-5	113	353	612	1,352

With respect to Classes C and J shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):

	1 year	3 years	5 years	10 years
Class C	$198	$612	$1,052	$2,275
Class J	108	337	585	1,294

Effective June 23, 2017, delete the Example section and replace with the following:

Example

This 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 then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. The calculation of costs takes into account any applicable contractual fee waivers and/or expense reimbursements for the period noted in the table above. 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 A	$491	$736	$1,000	$1,753
Class C	298	612	1,052	2,275
Class J	208	337	585	1,294
Institutional Class	88	274	477	1,061
Class R-1	176	545	939	2,041
Class R-2	163	505	871	1,900
Class R-3	145	449	776	1,702
Class R-4	125	390	676	1,489
Class R-5	113	353	612	1,352

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With respect to Classes C and J shares, you would pay the following expenses if you did not redeem your shares (all other classes would be the same as in the above example):

	1 year	3 years	5 years	10 years
Class C	$198	$612	$1,052	$2,275
Class J	108	337	585	1,294

Portfolio Turnover

As a fund of funds, the Fund does not pay transaction costs, such as commissions, when it buys and sells shares of underlying funds (or “turns over” its portfolio); however, the Fund does pay such transaction costs when it buys and sells other investments. Also, an underlying fund pays transaction costs when it buys and sells portfolio securities, and a higher portfolio turnover for the underlying fund may indicate higher transaction costs. These costs, which are not reflected in annual fund operating expenses or in the examples, affect the performance of the underlying fund and the Fund. During its most recent fiscal year, the Fund's portfolio turnover rate was 10.4% of the average value of its portfolio.

Principal Investment Strategies

The SAM Portfolios operate as funds of funds and invest principally in shares of Principal Funds, Inc. equity funds, fixed-income funds and specialty funds (“Underlying Funds”); the Sub-Advisor generally categorizes the Underlying Fund based on its investment profile. Each SAM Portfolio typically allocates its assets among Underlying Funds, and within predetermined percentage ranges, as determined by the Sub-Advisor in accordance with its outlook for the economy, the financial markets and the relative market valuations of the Underlying Funds. The diversification of the Portfolio is designed to moderate overall price volatility.

The Portfolio:

• Generally invests between 55% and 95% of its assets in fixed-income funds, and less than 40% in any one fixed-income fund; such fixed-income funds generally invest in fixed income instruments such as high yield securities (or “junk” bonds), real estate securities, mortgage-backed securities and other securitized products, government and government-sponsored securities, and corporate bonds;

• Generally invests between 5% and 45% of its assets in equity funds that invest in foreign and domestic securities, including value equity securities, and less than 30% in any one equity fund; and

• Generally invests less than 20% of its assets in specialty funds, and less than 20% in any one specialty fund; such specialty funds that generally offer unique combinations of traditional equity securities and fixed-income securities or that use alternative investment strategies that aim to offer diversification beyond traditional equity and fixed-income securities and include investments in such assets as infrastructure, commodities, currencies, and public timber companies.

The Portfolio may temporarily exceed these percentage ranges for short periods, and the Sub-Advisor may alter the percentage ranges when it deems appropriate.

Principal Risks

The value of your investment in the Portfolio changes with the value of the Portfolio's investments. Many factors affect that value, and it is possible to lose money by investing in the Portfolio. An investment in the Portfolio is not a deposit of a bank and is not insured or guaranteed by the Federal Deposit Insurance Corporation or any other government agency.

The principal risks of investing in the Portfolio that are inherent in the fund of funds are:

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Fund of Funds Risk. Portfolio shareholders bear indirectly their proportionate share of the expenses of other investment companies in which the Portfolio invests ("underlying funds"). The Portfolio's selection and weighting of asset classes and allocation of investments in underlying funds may cause it to underperform other funds with a similar investment objective. The Portfolio's performance and risks correspond directly to the performance and risks of the underlying funds in which it invests, proportionately in accordance with the weightings of such investments, and there is no assurance that the underlying funds will achieve their investment objectives. Management of the Portfolio entails potential conflicts of interest: the Portfolio invests in affiliated underlying funds; and the Advisor and its affiliates may earn different fees from different underlying funds and may have an incentive to allocate more Portfolio assets to underlying funds from which they receive higher fees.

Principal Risks due to the Portfolio's Investments in Underlying Funds

Equity Securities Risk. The value of equity securities could decline if the issuer's financial condition declines or in response to overall market and economic conditions. A fund's principal market segment(s) (such as market capitalization or style) may underperform other market segments or the equity markets as a whole.

• Value Stock Risk. Value stocks may continue to be undervalued by the market for extended periods, including the entire period during which the stock is held by the fund, or the events that the portfolio manager believed would cause the stock price to increase may not occur as anticipated or at all. Moreover, a stock judged to be undervalued actually may be appropriately priced at a low level and therefore would not be profitable for the fund.

Fixed-Income Securities Risk. Fixed-income securities are subject to interest rate risk and credit quality risk. The market value of fixed-income securities generally declines when interest rates rise, and an issuer of fixed-income securities could default on its payment obligations.

Foreign Currency Risk. Risks of investing in securities denominated in, or that trade in, foreign (non-U.S.) currencies include changes in foreign exchange rates and foreign exchange restrictions.

Foreign Securities Risk. The risks of foreign securities include loss of value as a result of: political or economic instability; nationalization, expropriation or confiscatory taxation; settlement delays; and limited government regulation (including less stringent reporting, accounting, and disclosure standards than are required of U.S. companies).

High Yield Securities Risk. High yield fixed-income securities (commonly referred to as "junk bonds") are subject to greater credit quality risk than higher rated fixed-income securities and should be considered speculative.

Portfolio Duration Risk. Portfolio duration is a measure of the expected life of a fixed-income security and its sensitivity to changes in interest rates. The longer a fund's average portfolio duration, the more sensitive the fund will be to changes in interest rates.

Real Estate Securities Risk. Investing in real estate securities subjects the fund to the risks associated with the real estate market (which are similar to the risks associated with direct ownership in real estate), including declines in real estate values, loss due to casualty or condemnation, property taxes, interest rate changes, increased expenses, cash flow of underlying real estate assets, regulatory changes (including zoning, land use and rents), and environmental problems, as well as to the risks related to the management skill and creditworthiness of the issuer.

Redemption Risk. A fund that serves as an underlying fund for a fund of funds is subject to certain risks. When a fund of funds reallocates or rebalances its investments, an underlying fund may experience relatively large redemptions or investments. These transactions may cause the underlying fund to sell portfolio securities to meet such redemptions, or to invest cash from such investments, at times it would not otherwise do so, and may as a result increase transaction costs and adversely affect underlying fund performance. Moreover, a fund of fund's redemptions or reallocations among share classes of an underlying fund may result in changes to the expense ratios of affected classes, which may increase the expenses paid by shareholders of the class that experienced the redemption.

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Securitized Products Risk. Investments in securitized products are subject to risks similar to traditional fixed income securities, such as credit, interest rate, liquidity, prepayment, extension, and default risk, as well as additional risks associated with the nature of the assets and the servicing of those assets. Unscheduled prepayments on securitized products may have to be reinvested at lower rates. A reduction in prepayments may increase the effective maturities of these securities, exposing them to the risk of decline in market value over time (extension risk).

U.S. Government Securities Risk. Yields available from U.S. government securities are generally lower than yields from many other fixed-income securities.

U.S. Government-Sponsored Securities Risk. Securities issued by U.S. government-sponsored or -chartered enterprises such as the Federal Home Loan Mortgage Corporation, the Federal National Mortgage Association, and the Federal Home Loan Banks are not issued or guaranteed by the U.S. Treasury.

Performance

The following information provides some indication of the risks of investing in the Portfolio. Past performance (before and after taxes) is not necessarily an indication of how the Portfolio will perform in the future. You may get updated performance information by calling 1-800-222-5852 or online at:

• For Classes A, C, J, and P - www.principalfunds.com.

• For Institutional Class and Classes R-1, R-2, R-3, R-4, and R-5 - www.principal.com.

The bar chart shows the investment returns of the Portfolio's Class A shares for each full calendar year of operations for 10 years (or, if shorter, the life of the Portfolio). These annual returns do not reflect sales charges on Class A shares; if they did, results would be lower. The table shows, for each share class of the Portfolio and for the last one, five, and ten calendar year periods (or, if shorter, the life of the Portfolio), how the Portfolio's average annual total returns compare with those of one or more broad measures of market performance.

The Portfolio commenced operations after succeeding to the operations of another fund on January 12, 2007. Performance for periods prior to that date is based on the performance of the predecessor fund. The predecessor fund's Class A shares commenced operations on July 25, 1996.

For periods prior to the inception date of Classes J, Institutional, R-1, R-2, R-3, R-4 and R-5 shares (January 16, 2007) and Class P shares (August 24, 2015), the performance shown in the table for Classes J, Institutional, P, R-1, R-2, R-3, R-4, and R-5 shares is based on the performance of the Portfolio's Class A shares, adjusted to reflect the respective fees and expenses of each class. Where this adjustment for fees and expenses results in performance for a newer class that is higher than the historical performance of the Class A shares, the historical performance of the Class A shares is used for the newer class (without respect to sales charges, if not applicable to the newer class). These adjustments for these newer classes result in performance for such periods that is no higher than the historical performance of the Class A shares.

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Total Returns as of December 31 (Class A shares)

Highest return for a quarter during the period of the bar chart above:	Q2 '09	10.74	%
Lowest return for a quarter during the period of the bar chart above:	Q4 '08	(7.04	)%

Average Annual Total Returns
For the periods ended December 31, 2016	1 Year	5 Years	10 Years
Class A Return Before Taxes	2.48%	4.61%	4.52%
Class A Return After Taxes on Distributions	1.33%	3.25%	3.11%
Class A Return After Taxes on Distribution and Sale of Fund Shares	1.58%	3.15%	3.08%
Class C Return Before Taxes	4.62%	4.63%	4.13%
Class J Return Before Taxes	5.55%	5.46%	4.82%
Class P Return Before Taxes	6.62%	5.46%	4.93%
Institutional Class Return Before Taxes	6.71%	5.75%	5.26%
Class R-1 Return Before Taxes	5.84%	4.85%	4.35%
Class R-2 Return Before Taxes	5.93%	4.98%	4.49%
Class R-3 Return Before Taxes	6.23%	5.18%	4.68%
Class R-4 Return Before Taxes	6.42%	5.37%	4.88%
Class R-5 Return Before Taxes	6.47%	5.49%	5.00%
Bloomberg Barclays U.S. Aggregate Bond Index (reflects no deduction for fees, expenses, or taxes)	2.65%	2.23%	4.34%
Russell 3000 Index (reflects no deduction for fees, expenses, or taxes)	12.74%	14.67%	7.07%
MSCI EAFE Index NR (reflects no deduction for fees, expenses, or taxes)	1.00%	6.53%	0.75%
SAM Flexible Income Blended Index (reflects no deduction for fees, expenses, or taxes)	4.67%	4.97%	4.98%

After-tax returns are calculated using the historical highest individual federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on an investor’s tax situation and may differ from those shown. The after-tax returns shown are not relevant to investors who hold their Fund shares through tax-deferred arrangements, such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Class A shares only and would be different for the other share classes.

Performance of a blended index shows how the Portfolio’s performance compares to a blend of indices with similar investment objectives. Performance of the components of the blended index are also shown. The weightings for SAM Flexible Income Blended Index are 75% Bloomberg Barclays U.S. Aggregate Bond Index, 20% Russell 3000^® Index and 5% MSCI EAFE Index NR. The custom or blended index returns reflect the allocation in effect for the time period(s) for which the fund returns are disclosed. Previous weightings or allocations of the custom or blended index are not restated.

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Management

Investment Advisor:

Principal Management Corporation

Sub-Advisor and Portfolio Managers:

Edge Asset Management, Inc.

• Charles D. Averill (since 2010), Portfolio Manager

• Todd A. Jablonski (since 2010), Chief Investment Officer and Portfolio Manager

Purchase and Sale of Fund Shares

Share Class	Investment Type	Purchase Minimum Per Fund
A, C, and J	Initial Investment	$1,000(1)
A, C, and J	For accounts with an Automatic Investment Plan (AIP)	$100
A, C, and J	Subsequent Investments	$100(1)(2)
P, Institutional, R-1, R-2, R-3, R-4, and R-5	There are no minimum initial or subsequent investment requirements for eligible purchases.	N/A

⁽¹⁾  Some exceptions apply; see "Purchase of Fund Shares - Minimum Investments" for more information.

⁽²⁾  For accounts with an AIP, the subsequent automatic investments must total $1,200 annually if the initial $1,000 minimum has not been met.

You may purchase or redeem shares on any business day (normally any day when the New York Stock Exchange is open for regular trading) through your plan, intermediary, or Financial Professional; by sending a written request to Principal Funds at P.O. Box 8024, Boston, MA 02266-8024 (regular mail) or 30 Dan Road, Canton, MA 02021-2809 (overnight mail); calling us at 1-800-222-5852; or accessing our website (www.principalfunds.com).

For retirement plan investors, effective as of the close of the New York Stock Exchange on January 31, 2017, Class R-1 and Class R-2 shares will no longer be available for purchase from new retirement plans except in limited circumstances. See Purchase of Fund Shares for additional information.

Tax Information

The Fund’s distributions you receive are generally subject to federal income tax as ordinary income or capital gain and may also be subject to state and local taxes, unless you are tax-exempt or your account is tax-deferred in which case your distributions would be taxed when withdrawn from the tax-deferred account.

Payments to Broker-Dealers and Other Financial Intermediaries

If you purchase the Fund through a broker-dealer or other financial intermediary (such as a bank, insurance company, investment adviser, etc.), 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 of the Fund over another share class. Ask your salesperson or visit your financial intermediary's website for more information.

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