Form N-1A Supplement

Jul. 31, 2024

Prospectus [Line Items]

Supplement to Prospectus [Text Block]

IMPORTANT NOTICE REGARDING CHANGE IN INVESTMENT POLICY

BLACKROCK FUNDS^SM

iShares Total U.S. Stock Market Index Fund

(the “Fund”)

Supplement dated November 20, 2025 to the Summary Prospectuses, the

Prospectuses, and the Statement of Additional Information (the “SAI”) of the Fund, each

dated November 27, 2024, as amended or supplemented to date

The Fund is updating its investment policy to indicate that it intends to be “diversified,” as defined in the Investment Company Act of 1940, as amended, in approximately the same proportion as its underlying index, the Russell 3000^® Index (the “Underlying Index”), is diversified. Shareholder approval will not be sought if the Fund crosses from diversified to non‑diversified status due solely to a change in the relative market capitalization or index weighting of the constituents of its Underlying Index.

Accordingly, the following changes are effective immediately:

The following is added at the end of the section of the Summary Prospectuses entitled “Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Investment Strategies of the Fund” and the section of the Prospectuses entitled “Fund Overview – Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Investment Strategies of the Fund”:

The Fund intends to be diversified in approximately the same proportion as the Underlying Index is diversified. The Fund may become “non‑diversified,” as defined in the Investment Company Act of 1940, as amended, solely as a result of a change in relative market capitalization or index weighting of one or more constituents of the Underlying Index. Shareholder approval will not be sought if the Fund becomes “non‑diversified” due solely to a change in the relative market capitalization or index weighting of one or more constituents of the Underlying Index.

The following is added to the section of the Summary Prospectuses entitled “Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Risks of Investing in the Fund” and the section of the Prospectuses entitled “Fund Overview – Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Risks of Investing in the Fund”:

• Non‑Diversification Risk — To the extent the Fund is non‑diversified, the Fund may invest a large percentage of its assets in securities or other instruments representing a small number of issuers or counterparties and thus may be more susceptible to the risks associated with these particular issuers or counterparties. As a result, the Fund’s performance may depend to a greater extent on the performance of a small number of issuers or counterparties, which may lead to more volatility in the Fund’s net asset value.

iShares Total U.S. Stock Market Index Fund

Prospectus [Line Items]

Supplement to Prospectus [Text Block]

IMPORTANT NOTICE REGARDING CHANGE IN INVESTMENT POLICY

BLACKROCK FUNDS^SM

iShares Total U.S. Stock Market Index Fund

(the “Fund”)

Supplement dated November 20, 2025 to the Summary Prospectuses, the

Prospectuses, and the Statement of Additional Information (the “SAI”) of the Fund, each

dated November 27, 2024, as amended or supplemented to date

The Fund is updating its investment policy to indicate that it intends to be “diversified,” as defined in the Investment Company Act of 1940, as amended, in approximately the same proportion as its underlying index, the Russell 3000^® Index (the “Underlying Index”), is diversified. Shareholder approval will not be sought if the Fund crosses from diversified to non‑diversified status due solely to a change in the relative market capitalization or index weighting of the constituents of its Underlying Index.

Accordingly, the following changes are effective immediately:

The following is added at the end of the section of the Summary Prospectuses entitled “Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Investment Strategies of the Fund” and the section of the Prospectuses entitled “Fund Overview – Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Investment Strategies of the Fund”:

The Fund intends to be diversified in approximately the same proportion as the Underlying Index is diversified. The Fund may become “non‑diversified,” as defined in the Investment Company Act of 1940, as amended, solely as a result of a change in relative market capitalization or index weighting of one or more constituents of the Underlying Index. Shareholder approval will not be sought if the Fund becomes “non‑diversified” due solely to a change in the relative market capitalization or index weighting of one or more constituents of the Underlying Index.

The following is added to the section of the Summary Prospectuses entitled “Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Risks of Investing in the Fund” and the section of the Prospectuses entitled “Fund Overview – Key Facts About iShares Total U.S. Stock Market Index Fund – Principal Risks of Investing in the Fund”:

• Non‑Diversification Risk — To the extent the Fund is non‑diversified, the Fund may invest a large percentage of its assets in securities or other instruments representing a small number of issuers or counterparties and thus may be more susceptible to the risks associated with these particular issuers or counterparties. As a result, the Fund’s performance may depend to a greater extent on the performance of a small number of issuers or counterparties, which may lead to more volatility in the Fund’s net asset value.