iShares MBS ETF
MBB
931 hedge funds and large institutions have $32B invested in iShares MBS ETF in 2025 Q1 according to their latest regulatory filings, with 109 funds opening new positions, 325 increasing their positions, 404 reducing their positions, and 74 closing their positions.
1,218% more call options, than puts
Call options by funds: $57.7M | Put options by funds: $4.38M
47% more first-time investments, than exits
New positions opened: 109 | Existing positions closed: 74
11% more funds holding in top 10
Funds holding in top 10: 61 → 68 (+7)
1% more funds holding
Funds holding: 922 → 931 (+9)
4% less capital invested
Capital invested by funds: $33.4B → $32B (-$1.43B)
5.12% less ownership
Funds ownership: 91.82% → 86.69% (-5.1%)
20% less repeat investments, than reductions
Existing positions increased: 325 | Existing positions reduced: 404
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
RH
RenaissanceRe Holdings
Pembroke,
Bermuda
|
+$264M |
| 2 |
LPL Financial
San Diego,
California
|
+$222M |
| 3 |
Fisher Asset Management
Camas,
Washington
|
+$124M |
| 4 |
UBS AM
Chicago,
Illinois
|
+$97.4M |
| 5 |
Jane Street
New York
|
+$83.9M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
Bank of America
Charlotte,
North Carolina
|
-$1.24B |
| 2 |
EP
Essential Planning
Portsmouth,
New Hampshire
|
-$301M |
| 3 |
Envestnet Asset Management
Chicago,
Illinois
|
-$199M |
| 4 |
Envestnet Portfolio Solutions
Chicago,
Illinois
|
-$111M |
| 5 |
RWP
RWA Wealth Partners
Newton,
Massachusetts
|
-$91.4M |
MBB Hedge Fund Activity: Q1 2025 in Review
931 of the 7,458 institutional investors tracked by Wall St. Rank reported a position in iShares MBS ETF (MBB) for Q1 2025, worth a combined $32B — down 4.3% from $33.4B a quarter earlier.
Buyers outnumbered sellers: 109 funds opened new MBB positions and 74 closed out — a net gain of 35 holders — while 325 added to existing stakes and 404 trimmed.
The largest buyer was RenaissanceRe Holdings, opening a new position worth an estimated $264M. The largest seller was Bank of America, cutting an estimated $1.24B.
- 931 institutional investors held iShares MBS ETF (MBB) as of Q1 2025, up from 922 in Q4 2024.
- Funds reported $32B of iShares MBS ETF stock for Q1 2025, down 4.3% quarter-over-quarter.
- 109 funds opened new iShares MBS ETF positions in Q1 2025 and 74 closed out, a net change of +35 holders.
- The largest iShares MBS ETF buyer in Q1 2025 was RenaissanceRe Holdings, an estimated $264M added.
- The largest iShares MBS ETF seller in Q1 2025 was Bank of America, an estimated $1.24B sold.
Based on aggregated 13F filings for Q1 2025.