iShares MBS ETF
1,024 hedge funds and large institutions have $33B invested in iShares MBS ETF in 2025 Q4 according to their latest regulatory filings, with 172 funds opening new positions, 476 increasing their positions, 282 reducing their positions, and 59 closing their positions.
192% more first-time investments, than exits
New positions opened: 172 | Existing positions closed: 59
69% more repeat investments, than reductions
Existing positions increased: 476 | Existing positions reduced: 282
66% more call options, than puts
Call options by funds: $4.4M | Put options by funds: $2.65M
10% more funds holding
Funds holding: 933 → 1,024 (+91)
0% more funds holding in top 10
Funds holding in top 10: 53 → 53 (0)
3.28% less ownership
Funds ownership: 87.94% → 84.65% (-3.3%)
9% less capital invested
Capital invested by funds: $36.5B → $33B (-$3.43B)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Bank of Montreal
Toronto,
Ontario, Canada
|
+$139M |
| 2 |
UBS AM
Chicago,
Illinois
|
+$138M |
| 3 |
LPL Financial
San Diego,
California
|
+$105M |
| 4 |
BPA
Beacon Pointe Advisors
Newport Beach,
California
|
+$76.4M |
| 5 |
TIAA Trust, National Association
Charlotte,
North Carolina
|
+$61.7M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Fisher Asset Management
Camas,
Washington
|
-$2.05B |
| 2 |
JP Morgan Chase
New York
|
-$1.58B |
| 3 |
Barclays
London,
United Kingdom
|
-$309M |
| 4 |
Prudential Financial
Newark,
New Jersey
|
-$139M |
| 5 |
Envestnet Asset Management
Chicago,
Illinois
|
-$137M |
MBB Hedge Fund Activity: Q4 2025 in Review
1,024 of the 8,284 institutional investors tracked by Wall St. Rank reported a position in iShares MBS ETF (MBB) for Q4 2025, worth a combined $33B — down 9.4% from $36.5B a quarter earlier.
Buyers outnumbered sellers: 172 funds opened new MBB positions and 59 closed out — a net gain of 113 holders — while 476 added to existing stakes and 282 trimmed.
The largest buyer was Bank of Montreal, adding an estimated $139M. The largest seller was Fisher Asset Management, cutting an estimated $2.05B.
- 1,024 institutional investors held iShares MBS ETF (MBB) as of Q4 2025, up from 933 in Q3 2025.
- Funds reported $33B of iShares MBS ETF stock for Q4 2025, down 9.4% quarter-over-quarter.
- 172 funds opened new iShares MBS ETF positions in Q4 2025 and 59 closed out, a net change of +113 holders.
- The largest iShares MBS ETF buyer in Q4 2025 was Bank of Montreal, an estimated $139M added.
- The largest iShares MBS ETF seller in Q4 2025 was Fisher Asset Management, an estimated $2.05B sold.
Based on aggregated 13F filings for Q4 2025.