MBB — iShares MBS ETF
Data updated: 2026-07-24
MBB — iShares MBS ETF data: holdings, portfolio allocation, expenses, performance, cashflows, risk and SEC filings. Long Securitized (MBS/ABS/CMBS) Bond · $38.74B AUM · 0.04% expense ratio · 6.8% 1-yr return. From SEC regulatory filings.
MBB Fund Overview
MBB — iShares MBS ETF is a US ETF managed by iSHARES TRUST, categorised as Long Securitized (MBS/ABS/CMBS) Bond. ABC INVEST provides holdings, performance, costs, cashflows, risk data, prospectus documents and SEC filings, sourced from SEC filings.
- Type: US ETF
- Manager: iSHARES TRUST
- Category: Long Securitized (MBS/ABS/CMBS) Bond
- Assets under management: $38.74B
- 1-year return: 6.8%
- Ticker: MBB
- SEC CIK: 0001100663
- SEC series ID: S000013702
- Share class ID: C000037544
MBB Holdings
Top 10 holdings of iShares MBS ETF by percentage of net assets, from the fund's latest SEC N-PORT filing.
| Holding | % of net assets |
|---|---|
| Blackrock Cash Funds | 6.77% |
| Freddie Mac | 1.05% |
| Government National Mortgage Association | 0.95% |
| Umbs, Tba | 0.83% |
| Government National Mortgage Association | 0.67% |
| Umbs, Tba | 0.64% |
| Government National Mortgage Association | 0.55% |
| Government National Mortgage Association | 0.54% |
| Government National Mortgage Association | 0.53% |
| Fannie Mae | 0.52% |
MBB Portfolio Allocation
Asset-class allocation of iShares MBS ETF by percentage of net assets, from the latest SEC N-PORT filing.
| Asset class | Allocation |
|---|---|
| Securitized | 98.1% |
| Cash & Equivalents | 6.8% |
MBB Performance
Total returns for MBB (as of 2026-08-01), from SEC filings.
| Period | Total return |
|---|---|
| YTD | 0.8% |
| 1 year | 6.8% |
| 3 years (annualised) | 4.3% |
| 5 years (annualised) | 0.4% |
MBB Risk Information
Risk metrics for MBB, derived from monthly returns in SEC filings.
- 1-year volatility (annualised): 3.4%
MBB Costs and Fees
MBB costs about $4 per $10,000 invested per year in fund expenses.
- Net expense ratio: 0.04%
- Gross expense ratio: 0.04%
- Portfolio turnover: 153%
- Brokerage commissions: 0.00 bps of average net assets (SEC N-CEN)
MBB Cashflows
Over the 12 months to 2026-02, iShares MBS ETF had net inflows of $944.43M, from monthly SEC N-PORT filings.
| Month | Net flow |
|---|---|
| 2026-02 | $0 |
| 2026-01 | $103.94M |
| 2025-12 | −$142.85M |
| 2025-11 | −$2.49B |
| 2025-10 | −$166.21M |
| 2025-09 | $380.70M |
MBB Debt Constituents
No individual debt constituents are reported in iShares MBS ETF's latest SEC N-PORT filing.
MBB Prospectus and SEC Filings
Official iShares MBS ETF filings on SEC EDGAR — prospectus, portfolio holdings and annual reports.
Related Funds
Other Long Securitized (MBS/ABS/CMBS) Bond funds tracked on ABC INVEST:
Data Sources
ABC INVEST compiles this page from public filings made to the U.S. Securities and Exchange Commission (SEC) through EDGAR: portfolio holdings and monthly cashflows from Form N-PORT, expenses and returns from fund prospectuses (Form 485BPOS) and the SEC DERA Risk/Return Summary data sets, annual data from Form N-CEN, and shareholder reports from Form N-CSR.