Prospectus by Investment Company (Form 497)

BlackRock ETF Trust

iShares U.S. Select Equity Active ETF

(the "Fund")

Supplement dated December 11, 2025 to the Statement of Additional Information ("SAI") of the Fund, dated August 28, 2025, as supplemented to date

Effective January 10, 2026, the Fund's SAI is amended as follows:

The section entitled "Investment Advisory, Administrative and Distribution Services-Administrator, Custodian and Transfer Agent" in the Fund's SAI is deleted in its entirety and replaced with the following:

Administrator, Custodian and Transfer Agent. State Street Bank and Trust Company ("State Street") serves as administrator, custodian and transfer agent for the Fund under the Master Services Agreement and related Service Schedule (the "Service Module"). State Street's principal address is One Congress Street, Suite 1, Boston, MA 02114. Pursuant to the Service Module for Fund Administration and Accounting Services with the Trust, State Street provides necessary administrative, legal, tax and accounting and financial reporting services for the maintenance and operations of the Trust and the Fund. In addition, State Street makes available the office space, equipment, personnel and facilities required to provide such services. Pursuant to the Service Module for Custodial Services with the Trust, State Street maintains, in separate accounts, cash, securities and other assets of the Trust and the Fund, keeps all necessary accounts and records and provides other services. State Street is required, upon the order of the Trust, to deliver securities held by State Street and to make payments for securities purchased by the Trust for the Fund. State Street is authorized to appoint certain foreign custodians or foreign custody managers for Fund investments outside the U.S. Pursuant to the Service Module for Transfer Agency Services with the Trust, State Street acts as a transfer agent for the Fund's authorized and issued shares of beneficial interest, and as dividend disbursing agent of the Trust. As compensation for these services, State Street receives certain out-of-pocket costs, transaction fees and asset-based fees which are accrued daily and paid monthly by BFA. BFA pays the compensation because it has agreed to pay these operating expenses under the Investment Advisory Agreement as described therein.

The section entitled "Creation and Redemption of Creation Units-Costs Associated with Creation Transactions" in the Fund's SAI is deleted in its entirety and replaced with the following:

Costs Associated with Creation Transactions. A standard creation transaction fee is imposed to offset the transfer and other transaction costs associated with the issuance of Creation Units.

Under an ETF Services Agreement, the Fund has retained BRIL, an affiliate of BFA, to perform certain order processing, Authorized Participant communications, and related services in connection with the issuance and redemption of Creation Units ("ETF Services"). BRIL will receive from an Authorized Participant a standard transaction fee on each creation order, which consists of (1) a fee for providing the ETF Services (the "ETF Servicing Fee") and (2) transfer, processing and other transaction costs charged by the Fund custodian in connection with the issuance of Creation Units for such creation order ("Custody Transaction Costs"). BRIL is entitled to retain the ETF Servicing Fee pursuant to the ETF Services Agreement, but BRIL will reimburse any Custody Transaction Costs to the Fund custodian according to the amounts invoiced by such custodian.

The ETF Servicing Fee is a flat fee per order regardless of the number of Creation Units being purchased, which amount will vary among different BlackRock-advised funds based on a number of factors, including the complexity of the order and the types of securities or instruments included in a fund's Creation Basket, among other variables. The ETF Servicing Fee may be equal to zero in certain instances, such as for creation transactions that consist solely of cash. The actual Custody Transaction Costs vary per order based on the number of trades, underlying markets and settlement locations associated with the issuance of a Creation Unit. The following table sets forth for the Fund an estimate of the creation transaction fee that would have been charged as of November 30, 2025 if the Fund had issued a Creation Unit on that date. The actual fee that would have been

charged to an Authorized Participant in connection with a creation order will vary over time depending on the factors discussed above, and may be higher than the fee set forth below.

In order to defray transaction expenses for the Fund and protect against possible shareholder dilution, if a creation transaction consists solely or partially of cash, the Authorized Participant may also be required to cover (up to the maximum amount shown below) certain brokerage, tax, foreign exchange, execution and other costs and expenses related to the execution of trades resulting from such transaction (which may, in certain instances, be based on a good faith estimate of transaction costs based on historical data or other inputs, at BlackRock's discretion, and may include part or all of the spread between the expected bid and offer side of the market and anticipated market impact). However, the Fund is not obligated to trade identical securities to the securities identified by BlackRock in estimating these transaction and other costs and expenses. In certain cases, BlackRock or an affiliate may determine in its discretion to deviate from the regular charge, subject to the maximum amounts shown below.

Authorized Participants will also bear the costs of transferring the Deposit Securities to the Fund. Certain fees/costs associated with creation transactions may be waived in certain circumstances. Investors who use the services of a broker or other financial intermediary to acquire Fund shares may be charged a fee for such services. 

The following table sets forth the Fund's estimated creation transaction fee as of November 30, 2025 and maximum additional charge (as described above):

The section entitled "Creation and Redemption of Creation Units-Costs Associated with Redemption Transactions" in the Fund's SAI is deleted in its entirety and replaced with the following:

Costs Associated with Redemption Transactions. A standard redemption transaction fee is imposed to offset transfer and other transaction costs that may be incurred by the Fund.

As described above, under an ETF Services Agreement, the Fund has retained BRIL, an affiliate of BFA, to perform certain ETF Services. BRIL will receive from an Authorized Participant a standard transaction fee on each redemption order, which consists of (1) the ETF Servicing Fee and (2) Custody Transaction Costs. BRIL is entitled to retain the ETF Servicing Fee pursuant to the ETF Services Agreement, but BRIL will reimburse any Custody Transaction Costs to the Fund custodian according to the amounts invoiced by such custodian.

The ETF Servicing Fee is a flat fee per order regardless of the number of Creation Units being redeemed, which amount will vary among different BlackRock-advised funds based on a number of factors, including the complexity of the order and the types of securities or instruments included in a fund's Redemption Basket, among other variables. The ETF Servicing Fee may be equal to zero in certain instances, such as for redemption transactions that consist solely of cash. The actual Custody Transaction Costs vary per order based on the number of trades, underlying markets, and settlement locations associated with the redemption of a Creation Unit. The following table sets forth for the Fund an estimate of the redemption transaction fee that would have been charged as of November 30, 2025 if the Fund had redeemed a Creation Unit on that date. The actual fee that would have been charged to an Authorized Participant in connection with a redemption order will vary over time depending on the factors discussed above, and may be higher than the fee set forth below.

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In order to defray transaction expenses for the Fund and protect against possible shareholder dilution, if a redemption transaction consists solely or partially of cash, the Authorized Participant may also be required to cover (up to the maximum amount shown below) certain brokerage, tax, foreign exchange, execution and other costs and expenses related to the execution of trades resulting from such transaction (which may, in certain instances, be based on a good faith estimate of transaction costs based on historical data or other inputs, at BlackRock's discretion, and may include part or all of the spread between the expected bid and offer side of the market and anticipated market impact). However, the Fund is not obligated to trade identical securities to the securities identified by BlackRock in estimating these transaction and other costs and expenses. In certain cases, BlackRock or an affiliate may determine in its discretion to deviate from the regular charge, subject to the maximum amounts shown below.

Authorized Participants will also bear the costs of transferring the Fund Securities from the Fund to their account on their order. Certain fees/costs associated with redemption transactions may be waived in certain circumstances. Investors who use the services of a broker or other financial intermediary to dispose of Fund shares may be charged a fee for such services.

The following table sets forth the Fund's estimated redemption transaction fee as of November 30, 2025 and maximum additional charge (as described above): 

Shareholders should retain this Supplement for future reference.

PRSAI-BELT-1225SUP

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