SEI INSTITUTIONAL INTERNATIONAL TRUST

Emerging Markets Debt Fund (SITEX)

Supplement Dated June 4, 2010 to the
Class A Shares Prospectus Dated January 31, 2010

This Supplement provides new and additional information beyond that contained in the Class A Shares Prospectus, and should be read in conjunction with such Prospectus.

Notification of Change in Investment Strategy and Risks of the Emerging Markets Debt Fund

At a meeting of the Board of Trustees held on May 12, 2010, the Board of Trustees of SEI Institutional International Trust approved a change to the investment strategy of the Emerging Markets Debt Fund (the "Fund"). Accordingly, the text of the "Principal Investment Strategies" section for the Fund is hereby deleted and replaced with the following:

Under normal circumstances, the Emerging Markets Debt Fund will invest at least 80% of its net assets in fixed income securities of emerging market issuers. The Fund will invest in debt securities of government, government-related and corporate issuers in emerging market countries, as well as entities organized to restructure the outstanding debt of such issuers. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SEI Investments Management Corporation (SIMC), the Fund's adviser. The Sub-Advisers will spread the Fund's holdings across a number of countries and industries to limit its exposure to a single emerging market economy and may not invest more than 25% of its assets in any single country. There are no restrictions on the Fund's average portfolio maturity, or on the maturity of any s pecific security. There is no minimum rating standard for the Fund's securities and the Fund's securities will generally be in the lower or lowest rating categories (including those below the fourth highest rating category by an NRSRO, commonly referred to as junk bonds).

The Sub-Advisers seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, the Sub-Advisers buy and sell currencies (i.e., take long or short positions) using futures, foreign currency forward contracts and other derivatives. The Fund may take long and short positions in foreign currencies in excess of the value of the Fund's assets denominated in a particular currency or when the Fund does not own assets denominated in that currency. The Fund may also engage in currency transactions in an attempt to take advantage of certain inefficiencies in the currency exchange market, to increase its exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes.

The Fund may purchase shares of ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly.

In addition, in the section entitled "Principal Risks" the following risk disclosures are hereby added:

Currency Risk—Due to the Fund's active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

Derivatives Risk—The risk that changes in the market value of securities held by the Fund, and of the derivative instruments relating to those securities, may not be proportionate. There may not be a liquid market for the Fund to sell a derivative instrument. Derivatives are also subject to the risk that a counterparty may default on its payment obligations to the Fund.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

SEI-F-665 (6/10)

SEI INSTITUTIONAL INTERNATIONAL TRUST

Emerging Markets Debt Fund

Supplement Dated June 4, 2010 to the
Class G Shares Prospectus Dated January 31, 2010

This Supplement provides new and additional information beyond that contained in the Class G Shares Prospectus, and should be read in conjunction with such Prospectus.

Notification of Change in Investment Strategy and Risks of the Emerging Markets Debt Fund

At a meeting of the Board of Trustees held on May 12, 2010, the Board of Trustees of SEI Institutional International Trust approved a change to the investment strategy of the Emerging Markets Debt Fund (the "Fund"). Accordingly, the text of the "Principal Investment Strategies" section for the Fund is hereby deleted and replaced with the following:

Under normal circumstances, the Emerging Markets Debt Fund will invest at least 80% of its net assets in fixed income securities of emerging market issuers. The Fund will invest in debt securities of government, government-related and corporate issuers in emerging market countries, as well as entities organized to restructure the outstanding debt of such issuers. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SEI Investments Management Corporation (SIMC), the Fund's adviser. The Sub-Advisers will spread the Fund's holdings across a number of countries and industries to limit its exposure to a single emerging market economy and may not invest more than 25% of its assets in any single country. There are no restrictions on the Fund's average portfolio maturity, or on the maturity of any s pecific security. There is no minimum rating standard for the Fund's securities and the Fund's securities will generally be in the lower or lowest rating categories (including those below the fourth highest rating category by an NRSRO, commonly referred to as junk bonds).

The Sub-Advisers seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, the Sub-Advisers buy and sell currencies (i.e., take long or short positions) using futures, foreign currency forward contracts and other derivatives. The Fund may take long and short positions in foreign currencies in excess of the value of the Fund's assets denominated in a particular currency or when the Fund does not own assets denominated in that currency. The Fund may also engage in currency transactions in an attempt to take advantage of certain inefficiencies in the currency exchange market, to increase its exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes.

The Fund may purchase shares of ETFs to gain exposure to a particular portion of the market while awaiting an opportunity to purchase securities directly.

In addition, in the section entitled "Principal Risks" the following risk disclosures are hereby added:

Currency Risk—Due to the Fund's active positions in currencies, it will be subject to the risk that currency exchange rates may fluctuate in response to, among other things, changes in interest rates, intervention (or failure to intervene) by U.S. or foreign governments, central banks or supranational entities, or by the imposition of currency controls or other political developments in the United States or abroad.

Derivatives Risk—The risk that changes in the market value of securities held by the Fund, and of the derivative instruments relating to those securities, may not be proportionate. There may not be a liquid market for the Fund to sell a derivative instrument. Derivatives are also subject to the risk that a counterparty may default on its payment obligations to the Fund.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

SEI-F-666 (6/10)

SEI INSTITUTIONAL INTERNATIONAL TRUST

Class A
Emerging Markets Debt Fund (SITEX)
Class G
Emerging Markets Debt Fund

Supplement Dated June 4, 2010
to the Statement of Additional Information Dated January 31, 2010

This Supplement provides new and additional information beyond that contained in the SAI, and should be read in conjunction with such SAI.

Notification of Change in Investment Strategy and Risks of the Emerging Markets Debt Fund

The SAI is hereby amended and supplemented to reflect the following changes in the investment strategy of the Emerging Markets Debt Fund. In the section entitled "Investment Objectives and Policies," the text relating to the sub-section entitled "Emerging Markets Debt Fund" is hereby deleted and replaced with the following:

EMERGING MARKETS DEBT FUND—The investment objective of the Emerging Markets Debt Fund is to maximize total return. There can be no assurance that the Fund will achieve its investment objective.

Under normal circumstances, the Emerging Markets Debt Fund will invest at least 80% of its net assets in fixed income securities of emerging market issuers. The Fund will invest in debt securities of government, government-related and corporate issuers in emerging market countries, as well as entities organized to restructure the outstanding debt of such issuers. The Fund uses a multi-manager approach, relying upon a number of Sub-Advisers with differing investment philosophies to manage portions of the Fund's portfolio under the general supervision of SEI Investments Management Corporation (SIMC), the Fund's adviser. The Sub-Advisers will spread the Fund's holdings across a number of countries and industries to limit its exposure to a single emerging market economy and may not invest more than 25% of its assets in any single country. There are no restrictions on the Fund's average portfolio maturity, or on the maturity of any specific secur ity. There is no minimum rating standard for the Fund's securities and the Fund's securities will generally be in the lower or lowest rating categories (including those below the fourth highest rating category by an NRSRO, commonly referred to as junk bonds).

The Sub-Advisers seek to enhance the Fund's return by actively managing the Fund's foreign currency exposure. In managing the Fund's currency exposure, the Sub-Advisers buy and sell currencies (i.e., take long or short positions) using futures, foreign currency forward contracts and other derivatives. The Fund may take long and short positions in foreign currencies in excess of the value of the Fund's assets denominated in a particular currency or when the Fund does not own assets denominated in that currency. The Fund may also engage in currency transactions in an attempt to take advantage of certain inefficiencies in the currency exchange market, to increase its exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another. In managing the Fund's currency exposure for foreign securities, the Sub-Advisers may buy and sell currencies for hedging or for speculative purposes.

In addition, in the section entitled "Description of Permitted Investments and Risk Factors" the text relating to the sub-section entitled "Forward Foreign Currency Contracts" is hereby deleted and replaced with the following:

FORWARD FOREIGN CURRENCY CONTRACTS—A forward foreign currency contract involves a negotiated obligation to purchase or sell a specific currency at a future date (with or without delivery required), which may be any fixed number of days from the date of the contract agreed upon by the parties, at a price set at the time of the contract. These contracts are traded in the interbank market conducted directly between currency traders (usually large, commercial banks) and their customers. A forward foreign currency contract generally has no deposit requirement, and no commissions are charged at any stage for trades.

Forward contracts generally may not be liquidated prior to the stated maturity date, although the parties to a contract may agree to enter into a second offsetting transaction with the same maturity, thereby fixing each party's profit or loss on the two transactions. Nevertheless, each position must still be maintained to maturity unless the parties separately agree on an earlier settlement date. As a result, a party to a forward contract must be prepared to perform its obligations under each such contract in full. Parties to a forward contract may also separately agree to extend the contract by "rolling" it over prior to the originally scheduled settlement date.

The Funds may use currency instruments as part of a hedging strategy, as described below.

Transaction Hedging. Transaction Hedging is entering into a currency transaction with respect to specific assets or liabilities of a Fund, which will generally arise in connection with the purchase or sale of its portfolio securities or the receipt of income therefrom. A Fund may enter into Transaction Hedging out of a desire to preserve the U.S. dollar price of a security when

it enters into a contract for the purchase or sale of a security denominated in a foreign currency. A Fund may be able to protect itself against possible losses resulting from changes in the relationship between the U.S. dollar and foreign currencies during the period between the date the security is purchased or sold and the date on which payment is made or received by entering into a forward contract for the purchase or sale, for a fixed amount of dollars, of the amount of the foreign currency involved in the underlying security transactions.

Position Hedging. A Fund may sell a non-U.S. currency and purchase U.S. currency to reduce exposure to the non-U.S. currency ("Position Hedging"). A Fund may use Position Hedging when an adviser reasonably believes that the currency of a particular foreign country may suffer a substantial decline against the U.S. dollar. A Fund may enter into a forward foreign currency contract to sell, for a fixed amount of dollars, the amount of foreign currency approximating the value of some or all of its portfolio securities denominated in such foreign currency. The precise matching of the forward foreign currency contract amount and the value of the portfolio securities involved may not have a perfect correlation since the future value of the securities hedged will change, as a consequence of the market, between the date the forward contract is entered into and the date it m atures. The projection of short-term currency market movement is difficult, and the successful execution of this short-term hedging strategy is uncertain.

Cross Hedges. A Fund may also cross-hedge currencies by entering into transactions to purchase or sell one or more currencies that are expected to decline in value relative to other currencies to which the Fund has or in which the Fund expects to have portfolio exposure.

Proxy Hedges. A Fund may also engage in proxy hedging. Proxy hedging is often used when the currency to which a Fund's portfolio is exposed is difficult to hedge or to hedge against the U.S. dollar. Proxy hedging entails entering into a forward contract to sell a currency whose changes in value are generally considered to be linked to a currency or currencies in which some or all of a Fund's portfolio securities are or are expected to be denominated, and to buy U.S. dollars. The amount of the contract would not exceed the value of the Fund's securities denominated in linked currencies.

In addition to the hedging transactions described above, the International Equity, International Fixed Income and Emerging Markets Debt Funds may also engage in currency transactions in an attempt to take advantage of certain inefficiencies in the currency exchange market, to increase their exposure to a foreign currency or to shift exposure to foreign currency fluctuations from one currency to another.

A Fund (except the International Equity, International Fixed Income and Emerging Markets Debt Funds) will not enter into a transaction to hedge currency exposure to an extent greater, after netting all transactions intended wholly or partially to offset other transactions, than the aggregate market value (at the time of entering into the transaction) of the securities held in its portfolio that are denominated or generally quoted in or currently convertible into such currency, other than with respect to proxy hedging as described above. The International Equity, International Fixed Income and Emerging Markets Debt Funds may take long and short positions in foreign currencies in excess of the value of the Fund's assets denominated in a particular currency or when the Fund does not own assets denominated in that currency.

The Funds may engage in non-deliverable forward transactions. A non-deliverable forward is a transaction that represents an agreement between a Fund and a counterparty (usually a commercial bank) to buy or sell a specified (notional) amount of a particular currency at an agreed upon foreign exchange rate on an agreed upon future date. The non-deliverable forward transaction position is closed using a fixing rate, as defined by the central bank in the country of the currency being traded, that is generally publicly stated within one or two days prior to the settlement date. Unlike other currency transactions, there is no physical delivery of the currency on the settlement of a non-deliverable forward transaction. Rather, a Fund and the counterparty agree to net the settlement by making a payment in U.S. dollars or another fully convertible currency that represents any differential between the foreign exchange rate agreed upon at the inception of the non-deliverable forward agreement and the actual exchange rate on the agreed upon future date. Thus, the actual gain or loss of a given non-deliverable forward transaction is calculated by multiplying the transaction's notional amount by the difference between the agreed upon forward exchange rate and the actual exchange rate when the transaction is completed.

The Funds may invest in options on foreign currencies and futures. Trading options on currency futures is relatively new, and the ability to establish and close out positions on such options is subject to the maintenance of a liquid market, which may not always be available. An option on a currency provides the purchaser, or "holder," with the right, but not the obligation, to purchase, in the case of a "call" option, or sell, in the case of a "put" option, a stated quantity of the underlying currency at a fixed exchange rate up to a stated expiration date (or, in the case of certain options, on such date). The holder generally pays a nonrefundable fee for the option, referred to as the "premium," but cannot lose more than this amount, plus related transaction costs. Thus, where a Fund is a holder of option contracts, such losses will be limited in absolute amount. In contrast to a forward contract, an option imposes a binding obligation onl y on the seller, or "writer." If the holder exercises the option, the writer is obligated to complete the transaction in the underlying currency. An option generally becomes worthless to the holder when it expires. In addition, in the context of an exchange-traded option, the writer is often required to deposit initial margin and may be required to increase the margin on deposit if the market moves against the writer's position. Options on currencies may be purchased in the over-the-counter market between commercial entities dealing directly with each other as principals. In purchasing

an over-the-counter currency option, the holder is subject to the risk of default by the writer and, for this reason, purchasers of options on currencies may require writers to post collateral or other forms of performance assurance.

The Funds may invest in foreign currency futures contracts. Buyers and sellers of currency futures are subject to the same risks that apply to the use of futures generally, which are described elsewhere in this SAI. Further, settlement of a currency futures contract for the purchase of most currencies must occur at a bank based in the issuing nation, which may subject a Fund to additional risk.

Risks. Currency transactions are subject to risks that are different from those of other portfolio transactions. Currency exchange rates may fluctuate based on factors extrinsic to that country's economy. Although forward foreign currency contracts and currency futures tend to minimize the risk of loss due to a decline in the value of the hedged currency, at the same time they may limit any potential gain which might result should the value of such currency increase. Because currency control is of great importance to the issuing governments and influences economic planning and policy, purchase and sales of currency and related instruments can be negatively affected by government exchange controls, blockages, and manipulations or exchange restrictions imposed by governments. These can result in losses to a Fund if it is unable to deliver or receive currency or fund s in settlement of obligations and could also cause hedges it has entered into to be rendered useless, resulting in full currency exposure as well as incurring transaction costs. Buyers and sellers of currency futures are subject to the same risks that apply to the use of futures generally. Further, settlement of a currency futures contract for the purchase of most currencies must occur at a bank based in the issuing nation. Trading options on currency futures are relatively new, and the ability to establish and close out positions on such options is subject to the maintenance of a liquid market, which may not always be available.

If any of the International Equity, International Fixed Income or Emerging Markets Debt Funds enters into currency transactions when it does not own assets denominated in that currency, the Fund's volatility may increase and losses on such transactions will not be offset by increases in the value of the Fund's assets.

Currency hedging involves some of the same risks and considerations as other transactions with similar instruments. Currency transactions can result in losses to a Fund if the currency being hedged fluctuates in value to a degree in a direction that is not anticipated. Furthermore, there is a risk that the perceived linkage between various currencies may not be present or may not be present during the particular time that a Fund is engaging in proxy hedging. Suitable hedging transactions may not be available in all circumstances. Hedging transactions may also eliminate any chance for a Fund to benefit from favorable fluctuations in relevant foreign currencies. If a Fund enters into a currency transaction, the Fund will "cover" its position as required by the 1940 Act.

PLEASE RETAIN THIS SUPPLEMENT FOR FUTURE REFERENCE

SEI-F-667 (6/10)