iShares MBS ETF holds 11,146 positions and $38.7B in net assets as of May 31, 2026. The largest: Fannie Mae 44.4%, Freddie Mac 28.1%, Government National Mortgage Association 23.0%, Blackrock CASH Funds 6.8%, Umbs, TBA 2.6%.

What is the expense ratio of MBB?

MBB costs 0.04% a year, from its prospectus.

MBBiShares MBS ETF

ETF · iSHARES TRUST

$92.10close Nov 9, 2026

The fund

Holdings as of May 31, 2026, filed with the SEC.

$38.7B

net assets, all share classes

0.04%

yearly cost, from the prospectus

11,146

positions on file

Growth of $100

Total return with dividends reinvested, month by month since September 2019.

$100$106

20192026

+6.8%

last 12 months

+4.3%

a year, over 3 years

+0.4%

a year, over 5 years

Largest holdings

The top 6 issuers of 11,146 positions, by share of the fund.

Fannie MaeMortgage-backed: 44.4%
Freddie MacMortgage-backed: 28.1%
Government National Mortgage AssociationMortgage-backed: 23.0%
Blackrock CASH FundsCash and short-term: 6.8%
Umbs, TBAMortgage-backed: 2.6%
Blackrock CASH Funds Treasury SL Agency SharesCash and short-term: 0.0%

Countries

Where the holdings are, by share of the fund.

United States104.9%

What it holds

By kind of asset.

Mortgage-backed98.1%
Cash and short-term6.8%

From the fund’s Form N-PORT for May 2026 (filed Jul 24, 2026) and its prospectus, via the SEC’s public data sets. Shares of net assets can sum above 100% where a fund holds cash collateral or derivatives.