Harbor International Small Cap Fund

Retirement Class HNISX

Institutional Class HAISX

Administrative Class HRISX

Investor Class HIISX

Summary Prospectus – March 1, 2025

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 harborcapital.com/prospectus. You can also get this information at no cost by calling 800-422-1050 or by sending an email request to funddocuments@harborcapital.com. If you purchase shares of the Fund through a financial intermediary, the prospectus and other information will also be available from your financial intermediary. The current prospectus and statement of additional information, dated March 1, 2025, as amended or supplemented from time to time, are incorporated by referenced into this summary prospectus and may be obtained, free of charge, at the website, phone number or email address noted above.

Investment Objective

The 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, hold and sell shares of the Fund. You may pay other fees, such as brokerage commissions and other fees to financial intermediaries, which are not reflected in the table and example below.

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

	Retirement Class	Institutional Class	Administrative Class	Investor Class
Management Fees	0.85%	0.85%	0.85%	0.85%
Distribution and Service (12b-1) Fees	None	None	0.25%	0.25%
Other Expenses1	0.11%	0.19%	0.19%	0.29%
Total Annual Fund Operating Expenses	0.96%	1.04%	1.29%	1.39%
Expense Reimbursement2	(0.14)%	(0.14)%	(0.14)%	(0.14)%
Total Annual Fund Operating Expenses After Expense Reimbursement2	0.82%	0.90%	1.15%	1.25%

1 Restated to reflect current fees for the Investor Class.

2 The Advisor has contractually agreed to limit the Fund’s operating expenses, excluding interest expense (if any), to 0.82%, 0.90%, 1.15%, and 1.25% for the Retirement Class, Institutional Class, Administrative Class, and Investor Class, respectively, through February 28, 2026. Only the Fund’s Board of Trustees may modify or terminate this agreement.

Expense 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. 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, under these assumptions, your costs would be:

	One Year	Three Years	Five Years	Ten Years
Retirement	$84	$292	$517	$1,165
Institutional	$92	$317	$560	$1,258
Administrative	$117	$395	$694	$1,544
Investor	$127	$426	$747	$1,656

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 may indicate higher transaction costs and may result in higher taxes when shares of the Fund are held in a taxable account. These costs, which are not reflected in the Annual Fund Operating Expenses or in the Expense Example, do affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 19%.

Principal Investment Strategy

The Fund invests primarily in equity securities, principally common and preferred stocks, of foreign companies. Under normal market conditions, the Fund invests at least 80% of its net assets, plus borrowings for investment purposes, in the securities of small cap companies. The Fund defines small cap companies as those with market capitalizations that fall within the range of the MSCI EAFE (Europe, Australasia and Far East) Small Cap (ND) Index at the time of purchase. As of December 31, 2024, the range of the Index was $105 million to $9.37 billion, but it is expected to change frequently.

The Subadvisor’s investment process utilizes a range of screening and idea sourcing methodologies to shrink the universe of securities to a manageable level. The Subadvisor primarily utilizes bottom-up research to identify companies with attractive valuations, as determined by the Subadvisor, while taking into account macro-economic considerations. The Subadvisor’s evaluation of companies includes an analysis of the corporate governance framework. The Subadvisor looks to identify companies that:

■

demonstrate traditional value metrics primarily on a price to book, price to earnings, and/or dividend yield basis;

■

have well-capitalized and transparent balance sheets and funding sources; and

■

they believe have business models that are undervalued by the market.

From time to time, the investment process may result in substantial investments in one or more sectors, geographic regions and/or countries.

The Subadvisor may sell or trim a holding when the investment thesis with respect to a holding is realized or the investment thesis is negatively impacted by macro-economic, industry or company-specific considerations. The Subadvisor may also sell or trim a holding in order to manage position-size risk and/or if a more attractive investment opportunity is identified. As part of its investment process, the Subadvisor considers environmental, social and governance (“ESG”) factors that it believes may have a material impact on an issuer and the value of its securities. As a result, the key ESG considerations may vary depending on the industry, sector, geographic region or other factors and the core business of each issuer.

Up to 15% of the Fund’s total assets may be invested in emerging market companies, which the Fund defines as those countries

Summary Prospectus

Harbor International Small Cap Fund

included in the MSCI Emerging Markets Index, which currently includes 24 countries located in the Americas, Europe, Middle East, Africa and Asia. The Fund also may invest in American Depositary Receipts (ADRs), European Depositary Receipts (EDRs), and Global Depository Receipts (GDRs) (collectively, “Depositary Receipts”). Depositary Receipts are certificates typically issued by a bank or trust company that represent ownership interests in securities issued by a foreign or domestic company. The Fund may invest in securities denominated in, and/or receiving revenues in, foreign currencies.

Principal Risks

There is no guarantee that the investment objective of the Fund will be achieved. Stocks fluctuate in price and the value of your investment in the Fund may go down. This means that you could lose money on your investment in the Fund or the Fund may not perform as well as other investment options. Principal risks impacting the Fund (in alphabetical order after the first five risks) include:

Foreign Securities Risk: An investment in the Fund is subject to special risks in addition to those of U.S. securities. These risks include heightened political and economic risks, greater volatility, currency fluctuations, higher transaction costs, delayed settlement, possible foreign controls on investment, possible sanctions by governmental bodies of other countries and less stringent investor protection and disclosure standards of foreign markets. Foreign securities are sometimes less liquid and harder to value than securities of U.S. issuers. The securities markets of many foreign countries are relatively small, with a limited number of companies representing a small number of industries. If foreign securities are denominated and traded in a foreign currency, the value of the Fund’s foreign holdings can be affected by currency exchange rates and exchange control regulations. The Fund’s investments in foreign securities may also be subject to foreign withholding taxes.

Global economies and financial markets are becoming increasingly interconnected, and conditions and events in one country, region or financial market may adversely impact issuers in a different country, region or financial market.

Small Cap Risk: The Fund’s performance may be more volatile because it invests primarily in issuers that are smaller companies. Smaller companies may have limited product lines, markets and financial resources. Securities of smaller companies are usually less stable in price and less liquid than those of larger, more established companies. Additionally, small cap stocks may fall out of favor relative to mid or large cap stocks, which may cause the Fund to underperform other equity funds that focus on mid or large cap stocks.

Value Style Risk: Securities issued by companies that may be perceived as undervalued may fail to appreciate for long periods of time and may never realize their full potential value. Over time, a value oriented investing style may go in and out of favor, which may cause the Fund to underperform other equity funds that use different investing styles.

Equity Risk: The values of equity or equity-related securities may decline due to general market conditions that are not specifically related to a particular company, such as real or perceived adverse economic conditions, changes in the general outlook for corporate earnings, changes in interest or currency rates or adverse investor sentiment generally. They may also decline due to factors that affect a particular industry or industries, such as labor shortages or increased production costs and competitive conditions within

an industry. Equity securities generally have greater price volatility than fixed income securities.

Market Risk: Securities markets are volatile and can decline significantly in response to adverse market, economic, political, regulatory or other developments, which may lower the value of securities held by the Fund, sometimes rapidly or unpredictably. Events such as war, acts of terrorism, social unrest, natural disasters, recessions, inflation, rapid interest rate changes, supply chain disruptions, sanctions, the spread of infectious illness or other public health threats could also significantly impact the Fund and its investments.

Depositary Receipts Risk: Depositary receipts are certificates evidencing ownership of shares of a foreign issuer. These certificates are issued by depository banks and generally trade on an established market in the U.S. or elsewhere. The underlying shares are held in trust by a custodian bank or similar financial institution. The depository bank may not have physical custody of the underlying securities at all times and may charge fees for various services, including forwarding dividends and interest and corporate actions. Depositary receipts are alternatives to directly purchasing the underlying foreign securities in their national markets and currencies. The issuers of depositary receipts may discontinue issuing new depositary receipts and withdraw existing depositary receipts at any time, which may result in costs and delays in the distribution of the underlying assets to the Fund and may negatively impact the Fund’s performance. Depositary receipts are subject to the risks associated with investing directly in foreign securities.

Emerging Market Risk: Foreign securities risks are more significant in emerging market countries. These countries may have relatively unstable governments and less-established market economies than developed countries. Emerging markets may face greater social, economic, regulatory and political uncertainties. These risks make emerging market securities more volatile and less liquid than securities issued in more developed countries. Securities exchanges in emerging markets may suspend listed securities from trading for substantially longer periods of time than exchanges in developed markets, including for periods of a year or longer. If the Fund is holding a suspended security, that security would become completely illiquid as the Fund would not be able to dispose of the security until the suspension is lifted. In such instances, it can also be difficult to determine an appropriate valuation for the security because of a lack of trading and uncertainty as to when trading may resume.

ESG Factors Risk: The consideration of ESG factors by the Subadvisor and/or Advisor, as applicable, could cause the Fund to perform differently than other funds. ESG factors are not the only consideration used by the Subadvisor and/or Advisor, as applicable, in making investment decisions for the Fund and the Fund may invest in a company that scores poorly on ESG factors if it scores well on other criteria. ESG factors may not be considered for every investment decision.

Foreign Currency Risk: As a result of the Fund’s investments in securities denominated in, and/or receiving revenues in, foreign currencies, the Fund will be subject to currency risk. Currency risk is the risk that foreign currencies will decline in value relative to the U.S. dollar or, in the case of hedging positions, that the U.S. dollar will decline in value relative to the currency hedged. In either event, the dollar value of an investment in the Fund would be adversely affected.

Geographic Focus Risk: The Fund may invest a substantial amount of its assets in securities of issuers located in a single country or geographic region. As a result, any changes to the regulatory, political, social or economic conditions in such country or geographic region will generally have greater impact on the Fund

Summary Prospectus

Harbor International Small Cap Fund

than such changes would have on a more geographically diversified fund and may result in increased volatility and greater losses.

Issuer Risk: An adverse event affecting a particular issuer in which the Fund is invested, such as an unfavorable earnings report, may depress the value of that issuer’s securities, sometimes rapidly or unpredictably.

Preferred Stock Risk: Preferred stocks in which the Fund may invest are sensitive to interest rate changes, and are also subject to equity risk, which is the risk that stock prices will fall over short or extended periods of time. The rights of preferred stocks on the distribution of a company’s assets in the event of a liquidation are generally subordinate to the rights associated with a company’s debt securities.

Sector Risk: Because the Fund may, from time to time, be more heavily invested in particular sectors, the value of its shares may be especially sensitive to factors and economic risks that specifically affect those sectors. As a result, the Fund’s share price may fluctuate more widely than the value of shares of a mutual fund that invests in a broader range of sectors.

Selection Risk: The Subadvisor’s judgment about the attractiveness, value and growth potential of a particular security may be incorrect, which may cause the Fund to underperform. Additionally, the Subadvisor and/or Advisor, as applicable, potentially will be prevented from executing investment decisions at an advantageous time or price as a result of domestic or global market disruptions, particularly disruptions causing heightened market volatility and reduced market liquidity, as well as increased or changing regulations. Thus, investments that a Subadvisor and/or Advisor, as applicable, believes represent an attractive opportunity or in which the Fund seeks to obtain exposure may be unavailable entirely or in the specific quantities or prices sought by a Subadvisor and/or Advisor, as applicable, and the Fund may need to obtain the exposure through less advantageous or indirect investments or forgo the investment at the time.

Performance

Effective May 23, 2019, Cedar Street Asset Management LLC (“Cedar Street”) became the Fund’s Subadvisor. Performance prior to that date is not attributable to Cedar Street.

The following bar chart and tables are intended to help you understand the risks and potential rewards of investing in the Fund. The bar chart shows how the performance of the Fund’s Institutional Class has varied from one calendar year to another over the periods shown. The table shows how the Fund’s average annual total returns of the share classes presented compare to a broad measure of market performance and an additional index over time. Please note that the Fund’s past performance (before and after taxes) is not necessarily an indication of how the Fund will perform in the future. To obtain updated performance information please visit the Fund’s website at harborcapital.com or call 800-422-1050.

Calendar Year Total Returns for Institutional Class Shares

During the time periods shown in the bar chart, the Fund’s highest and lowest returns for a calendar quarter were:

	Total Returns	Quarter/Year
Best Quarter	21.41%	Q4 2020
Worst Quarter	-29.16%	Q1 2020

Summary Prospectus

Harbor International Small Cap Fund

Average Annual Total Returns — As of December 31, 2024

	One Year	Annualized			Inception Date
	One Year	Five Years	Ten Years	Since Inception	Inception Date
Harbor International Small Cap Fund
Retirement Class Before Taxes	-0.78%	4.78%	N/A	6.89%	02-01-2016
Institutional Class Before Taxes	-0.77%	4.71%	N/A	6.82%	02-01-2016
After Taxes on Distributions	-1.70%	3.92%	N/A	6.17%
After Taxes on Distributions and Sale of Fund Shares	0.60%	3.74%	N/A	5.53%
Administrative Class Before Taxes	-0.97%	4.45%	N/A	6.55%	02-01-2016
Investor Class Before Taxes	-1.13%	4.34%	N/A	6.43%	02-01-2016
Comparative Indices (reflects no deduction for fees, expenses or taxes)
MSCI EAFE (ND)^	3.82%	4.73%	N/A	6.74%
MSCI EAFE Small Cap (ND)^^	1.82%	2.30%	N/A	5.94%

Since Inception return based on the inception date of the Institutional Class shares. This index represents a broad measure of market performance.

^^Since Inception return based on the inception date of the Institutional Class shares. The Advisor considers this index to be representative of the Fund’s principal investment strategies and therefore the appropriate benchmark index for the Fund for performance comparison purposes.

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 will depend on a shareholder’s individual tax situation and may differ from those shown. The after-tax returns shown are not relevant to tax-exempt shareholders or shareholders who hold their Fund shares through a tax-deferred arrangement, such as a 401(k) plan or individual retirement account. In some cases, average annual total return “After Taxes on Distributions and Sale of Fund Shares” may exceed the return “Before Taxes” and/or “After Taxes on Distributions” due to an assumed tax benefit for any losses on a sale of Fund shares at the end of the measurement period.After-tax returns are shown for Institutional Class shares only. After-tax returns for each of the Retirement, Administrative, and Investor Class of shares will vary.

Portfolio Management

Investment Advisor

Harbor Capital Advisors, Inc.

Subadvisor

Cedar Street has subadvised the Fund since 2019.

Portfolio Managers

The portfolio managers are jointly and primarily responsible for the day-to-day investment decision making for the Fund.

Jonathan P. Brodsky

Cedar Street

Mr. Brodsky, Founder and Principal at Cedar Street, has co-managed the Fund since 2019.

Waldemar A. Mozes

Cedar Street

Mr. Mozes is the Director of Investments, Portfolio Manager, and Partner at Cedar Street and has co-managed the Fund since 2019.

Summary Prospectus

Harbor International Small Cap Fund

Buying and Selling Fund Shares

Shareholders may purchase or sell (redeem) Fund shares on any business day (normally any day the New York Stock Exchange is open). You may conduct transactions by mail, by telephone or through our website.

By Mail	Harbor Funds P.O. Box 804660 Chicago, IL 60680-4108
By Telephone	800-422-1050
By Visiting Our Website	harborcapital.com

Investors who wish to purchase, exchange or redeem shares held through a financial intermediary should contact the financial intermediary directly.

The minimum initial investment amounts are shown below. The minimums may be reduced or waived in some cases. There are no minimums for subsequent investments.

Type of Account	Retirement Class1	Institutional Class	Administrative Class2	Investor Class
Regular	$1,000,000	$50,000	$50,000	$2,500
Individual Retirement Account (IRA)	$1,000,000	$50,000	N/A	$1,000
Custodial (UGMA/UTMA)	$1,000,000	$50,000	N/A	$1,000

1 There is no minimum investment for (1) employer-sponsored group retirement or benefit plans (with more than one participant) that maintain accounts with Harbor Funds at an omnibus or plan level, including: (i) plans established under Internal Revenue Code Sections 401(a), 403(b) or 457, (ii) profit-sharing plans, cash balance plans and money purchase pension plans, (iii) non-qualified deferred compensation plans, and (iv) retiree health benefit plans; and (2) certain wrap or model-driven asset allocation program accounts for the benefit of clients of financial intermediaries, as approved by the Distributor.

2 Limited only to employer-sponsored retirement or benefit plans and financial intermediaries. There is no minimum investment for employer-sponsored retirement or benefit plans.

Tax Information

Distributions you receive from the Fund are subject to federal income tax and may also be subject to state and local taxes. These distributions will generally be taxed as ordinary income or capital gains, unless you are investing through a tax-deferred retirement account, such as a 401(k) plan or individual retirement account. Investments in tax-deferred accounts may be subject to tax when they are withdrawn.

Payments to Broker-Dealers and Other Financial Intermediaries

The Fund, the Advisor and/or its related companies have in the past and could in the future pay intermediaries, which may include banks, broker-dealers, or financial professionals, for marketing activities and presentations, educational training programs, conferences, the development of technology platforms and reporting systems and data or other services related to the sale of Fund shares and related services. These payments create a conflict of interest by influencing the broker-dealer or other intermediary and your sales representative to recommend the Fund over another investment. Ask your sales representative or visit your financial intermediary’s website for more information.

Summary Prospectus

HARBOR INTERNATIONAL SMALL CAP FUND

March 1, 2025

Retirement Class	Institutional Class	Administrative Class	Investor Class

HNISX	HAISX	HRISX	HIISX

HF.SP.INTS.0325

111 South Wacker Drive, 34th Floor

Chicago, IL 60606-4302