iShares MBS ETF
1,031 hedge funds and large institutions have $34.9B invested in iShares MBS ETF in 2026 Q1 according to their latest regulatory filings, with 117 funds opening new positions, 512 increasing their positions, 286 reducing their positions, and 91 closing their positions.
185% more call options, than puts
Call options by funds: $5.88M | Put options by funds: $2.06M
79% more repeat investments, than reductions
Existing positions increased: 512 | Existing positions reduced: 286
29% more first-time investments, than exits
New positions opened: 117 | Existing positions closed: 91
17% more funds holding in top 10
Funds holding in top 10: 53 → 62 (+9)
6% more capital invested
Capital invested by funds: $33B → $34.9B (+$1.89B)
5.56% more ownership
Funds ownership: 84.65% → 90.22% (+5.6%)
1% more funds holding
Funds holding: 1,024 → 1,031 (+7)
Top Buyers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
UBS Group
Zurich,
Switzerland
|
+$1.9B |
| 2 |
UBS AM
Chicago,
Illinois
|
+$273M |
| 3 |
Envestnet Asset Management
Chicago,
Illinois
|
+$272M |
| 4 |
JP Morgan Chase
New York
|
+$196M |
| 5 |
Truist Financial
Charlotte,
North Carolina
|
+$176M |
Top Sellers
| Rank | Fund | Capital Flow |
|---|---|---|
| 1 |
TIAA Trust, National Association
Charlotte,
North Carolina
|
-$2.43B |
| 2 |
Bank of America
Charlotte,
North Carolina
|
-$463M |
| 3 |
RH
RenaissanceRe Holdings
Pembroke,
Bermuda
|
-$367M |
| 4 |
Barclays
London,
United Kingdom
|
-$237M |
| 5 |
Ameriprise
Minneapolis,
Minnesota
|
-$140M |
MBB Hedge Fund Activity: Q1 2026 in Review
1,031 of the 8,208 institutional investors tracked by Wall St. Rank reported a position in iShares MBS ETF (MBB) for Q1 2026, worth a combined $34.9B — up 5.7% from $33B a quarter earlier.
Buyers outnumbered sellers: 117 funds opened new MBB positions and 91 closed out — a net gain of 26 holders — while 512 added to existing stakes and 286 trimmed.
The largest buyer was UBS Group, adding an estimated $1.9B. The largest seller was TIAA Trust, National Association, cutting an estimated $2.43B.
- 1,031 institutional investors held iShares MBS ETF (MBB) as of Q1 2026, up from 1,024 in Q4 2025.
- Funds reported $34.9B of iShares MBS ETF stock for Q1 2026, up 5.7% quarter-over-quarter.
- 117 funds opened new iShares MBS ETF positions in Q1 2026 and 91 closed out, a net change of +26 holders.
- The largest iShares MBS ETF buyer in Q1 2026 was UBS Group, an estimated $1.9B added.
- The largest iShares MBS ETF seller in Q1 2026 was TIAA Trust, National Association, an estimated $2.43B sold.
Based on aggregated 13F filings for Q1 2026.