iShares MBS ETF
932 hedge funds and large institutions have $36.5B invested in iShares MBS ETF in 2025 Q3 according to their latest regulatory filings, with 97 funds opening new positions, 449 increasing their positions, 285 reducing their positions, and 83 closing their positions.
338% more call options, than puts
Call options by funds: $12.3M | Put options by funds: $2.81M
58% more repeat investments, than reductions
Existing positions increased: 449 | Existing positions reduced: 285
17% more first-time investments, than exits
New positions opened: 97 | Existing positions closed: 83
6% more capital invested
Capital invested by funds: $34.4B → $36.5B (+$2.05B)
0.5% more ownership
Funds ownership: 87.43% → 87.93% (+0.5%)
1% less funds holding
Funds holding: 941 → 932 (-9)
10% less funds holding in top 10
Funds holding in top 10: 59 → 53 (-6)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Bank of America
Charlotte,
North Carolina
|
+$711M |
| 2 |
Barclays
London,
United Kingdom
|
+$312M |
| 3 |
LPL Financial
San Diego,
California
|
+$136M |
| 4 |
TIAA Trust, National Association
Charlotte,
North Carolina
|
+$131M |
| 5 |
Fisher Asset Management
Camas,
Washington
|
+$113M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Royal Bank of Canada
Toronto,
Ontario, Canada
|
-$102M |
| 2 |
UBS AM
Chicago,
Illinois
|
-$97.7M |
| 3 |
Bank of New York Mellon
New York
|
-$96.9M |
| 4 |
AssetMark Inc
Concord,
California
|
-$80.1M |
| 5 |
Sumitomo Mitsui Trust Group
Minato-Ku, Tokyo,
Japan
|
-$51.1M |
MBB Hedge Fund Activity: Q3 2025 in Review
932 of the 7,638 institutional investors tracked by Wall St. Rank reported a position in iShares MBS ETF (MBB) for Q3 2025, worth a combined $36.5B — up 6% from $34.4B a quarter earlier.
Buyers outnumbered sellers: 97 funds opened new MBB positions and 83 closed out — a net gain of 14 holders — while 449 added to existing stakes and 285 trimmed.
The largest buyer was Bank of America, adding an estimated $711M. The largest seller was Royal Bank of Canada, cutting an estimated $102M.
- 932 institutional investors held iShares MBS ETF (MBB) as of Q3 2025, down from 941 in Q2 2025.
- Funds reported $36.5B of iShares MBS ETF stock for Q3 2025, up 6% quarter-over-quarter.
- 97 funds opened new iShares MBS ETF positions in Q3 2025 and 83 closed out, a net change of +14 holders.
- The largest iShares MBS ETF buyer in Q3 2025 was Bank of America, an estimated $711M added.
- The largest iShares MBS ETF seller in Q3 2025 was Royal Bank of Canada, an estimated $102M sold.
Based on aggregated 13F filings for Q3 2025.