Prospectus by Investment Company (Form 497)

BLACKROCK ETF TRUST II

iShares Total Return Active ETF

(the "Fund")

Supplement dated November 12, 2025 (the "Supplement") to the Fund's Statement of Additional Information (the "SAI"), dated November 27, 2024, as supplemented to date

The following changes are made to the Fund's SAI:

The sections of the SAI entitled "Investment Advisory, Administrative and Distribution Services - Portfolio Managers" and "Investment Advisory, Administrative and Distribution Services - Portfolio Manager Compensation Overview" are deleted in their entirety and replaced with the following:

Portfolio Managers. As of July 31, 2024 (except as otherwise noted), the individuals named as Portfolio Managers in the Fund's Prospectus were also jointly and primarily responsible for the day-to-day management of other BlackRock funds and certain other types of portfolios and/or accounts as follows:

Rick Rieder

Russell Brownback¹

Chi Chen

Siddharth Mehta¹

Sam Summers¹

Pursuant to BFA's policy, investment opportunities are allocated equitably among the Fund and other portfolios and accounts. For example, under certain circumstances, an investment opportunity may be restricted due to limited supply in the market, legal constraints or other factors, in which event the investment opportunity will be allocated equitably among those portfolios and accounts, including the Fund, seeking such investment opportunity. As a consequence, from time to time the Fund may receive a smaller allocation of an investment opportunity than it would have if the Portfolio Managers and BFA and its affiliates did not manage other portfolios or accounts.

Like the Fund, the other portfolios or accounts for which the Portfolio Managers are jointly and primarily responsible for the day-to-day portfolio management generally pay an asset-based fee to BFA or its affiliates, as applicable, for its advisory services. One or more of those other portfolios or accounts, however, may pay BFA or its affiliates a performance-based fee in lieu of, or in addition to, an asset-based fee for its advisory services. A portfolio or account with a performance-based fee would pay BFA or its affiliates a portion of that portfolio's or account's gains, or would pay BFA or its affiliates more for its services than would otherwise be the case if BFA or any of its affiliates meets or exceeds specified performance targets. Performance-based fee arrangements could present an incentive for BFA or its affiliates to devote greater resources, and allocate more investment opportunities, to the portfolios or accounts that have those fee arrangements, relative to other portfolios or accounts, in order to earn larger fees. Although BFA and each of its affiliates have an obligation to allocate resources and opportunities equitably among portfolios and accounts and intend to do so, shareholders of the Fund should be aware that, as with any group of portfolios and accounts managed by an investment adviser and/or its affiliates pursuant to varying fee arrangements, including performance-based fee arrangements, there is the potential for a conflict of interest, which may result in the Portfolio Managers favoring those portfolios or accounts with performance-based fee arrangements.

The tables below show, for each Portfolio Manager, the number of portfolios or accounts of the types set forth in the above tables and the aggregate of total assets in those portfolios or accounts with respect to which the investment management fees are based on the performance of those portfolios or accounts as of July 31, 2024 (except as otherwise noted):

Rick Rieder

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Russell Brownback¹

Chi Chen

Siddharth Mehta¹

Sam Summers¹

Portfolio Manager Compensation Overview

BlackRock, Inc.'s financial arrangements with its portfolio managers, its competitive compensation and its career path emphasis at all levels reflect the value senior management places on key resources. Compensation may

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include a variety of components and may vary from year to year based on a number of factors. The principal components of compensation include a base salary, a performance-based discretionary bonus, participation in various benefits programs and one or more of the incentive compensation programs established by BlackRock, Inc.

The discussion below describes the compensations of Mr. Rieder and Ms. Chen as of July 31, 2024, and the compensations of Messrs. Brownback, Mehta and Summers as of July 31, 2025.

Base compensation. Generally, portfolio managers receive base compensation based on their position with the firm.

Discretionary Incentive Compensation. Discretionary incentive compensation is a function of several components: the performance of BlackRock, Inc., the performance of the portfolio manager's group within BlackRock, the investment performance, including risk-adjusted returns, of the firm's assets under management or supervision by that portfolio manager relative to predetermined benchmarks, and the individual's performance and contribution to the overall performance of these portfolios and BlackRock. In most cases, these benchmarks are the same as the benchmark or benchmarks against which the performance of the funds or other accounts managed by the portfolio managers are measured. Among other things, BlackRock's Chief Investment Officers make a subjective determination with respect to each portfolio manager's compensation based on the performance of the funds and other accounts managed by each portfolio manager relative to the various benchmarks. Performance of fixed income funds is measured on a pre-tax and/or after-tax basis over various time periods including 1-, 3- and 5- year periods, as applicable. With respect to these portfolio managers, such benchmarks for the Fund and other accounts are:

Distribution of Discretionary Incentive Compensation. Discretionary incentive compensation is distributed to portfolio managers in a combination of cash, deferred BlackRock, Inc. stock awards, and/or deferred cash awards that notionally track the return of certain BlackRock investment products.

Portfolio managers receive their annual discretionary incentive compensation in the form of cash. Portfolio managers whose total compensation is above a specified threshold also receive deferred BlackRock, Inc. stock awards annually as part of their discretionary incentive compensation. Paying a portion of discretionary incentive compensation in the form of deferred BlackRock, Inc. stock puts compensation earned by a portfolio manager for a given year "at risk" based on BlackRock's ability to sustain and improve its performance over future periods. In some cases, additional deferred BlackRock, Inc. stock may be granted to certain key employees as part of a long-term incentive award to aid in retention, align interests with long-term shareholders and motivate performance. Deferred BlackRock, Inc. stock awards are generally granted in the form of BlackRock, Inc. restricted stock units that vest pursuant to the terms of the applicable plan and, once vested, settle in BlackRock, Inc. common stock. The portfolio managers of this Fund have deferred BlackRock, Inc. stock awards.

For certain portfolio managers, a portion of the discretionary incentive compensation is also distributed in the form of deferred cash awards that notionally track the returns of select BlackRock investment products they manage, which provides direct alignment of portfolio manager discretionary incentive compensation with investment product results. Deferred cash awards vest ratably over a number of years and, once vested, settle in

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the form of cash. Only portfolio managers who manage specified products and whose total compensation is above a specified threshold are eligible to participate in the deferred cash award program.

Other Compensation Benefits. In addition to base salary and discretionary incentive compensation, portfolio managers may be eligible to receive or participate in one or more of the following:

Incentive Savings Plans - BlackRock, Inc. has created a variety of incentive savings plans in which BlackRock, Inc. employees are eligible to participate, including a 401(k) plan, the BlackRock Retirement Savings Plan ("RSP"), and the BlackRock Employee Stock Purchase Plan ("ESPP"). The employer contribution components of the RSP include a company match equal to 50% of the first 8% of eligible pay contributed to the plan capped at $5,000 per year, and a company retirement contribution equal to 3-5% of eligible compensation up to the Internal Revenue Service (the "IRS") limit ($350,000 for 2025). The RSP offers a range of investment options, including registered investment companies and collective investment funds managed by the firm. BlackRock, Inc. contributions follow the investment direction set by participants for their own contributions or, absent participant investment direction, are invested into a target date fund that corresponds to, or is closest to, the year in which the participant attains age 65. The ESPP allows for investment in BlackRock, Inc. common stock at a 5% discount on the fair market value of the stock on the purchase date. Annual participation in the ESPP is limited to the purchase of 1,000 shares of common stock or a dollar value of $25,000 based on its fair market value on the purchase date. All of the eligible portfolio managers are eligible to participate in these plans.

As of July 31, 2024, Mr. Rieder and Ms. Chen did not beneficially own shares of the Fund. As of July 31, 2025, Messrs. Brownback, Mehta and Summers did not beneficially own shares of the Fund.

Shareholders should retain this Supplement for future reference.

SAI-TRETF-1125SUP

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