CSTL Institutional Ownership
Who owns Castle Biosciences Inc and what the big funds did with it last quarter, from every SEC 13F filing. 176 funds reported holding CSTL at Jun 30, 2026, together owning 88.7% of the company.
- ▲98 buying vs 84 selling
- ▼Held by funds -0.9 pts
- ▼Funds holding -10
- ●Superinvestors: 2 added, 2 cut
- ●Put/call not meaningful
What the filings show, not a forecast. Positions can be up to 45 days old and leave out short sales.
Funds holding and ownership
8 quartersQuarter over quarter
all 13F filers| Q2 2026 | This quarter | Q1 2026 | Change |
|---|---|---|---|
| Funds holding | 176 | 186 | −5.4% |
| In funds' top 10 | 0 | 1 | −100.0% |
| 13F shares | 27.3M | 27.6M | −1.0% |
| Held by funds | 88.7% | 89.6% | −0.9 pts |
| New positions | 21 | 23 | −8.7% |
| Increased | 77 | 72 | +6.9% |
| Reduced | 54 | 60 | −10.0% |
| Sold out | 30 | 36 | −16.7% |
| Calls (shares) | 0 | 0 | – |
| Puts (shares) | 0 | 0 | – |
| Put/call ratio | – | – | – |
Buyers vs sellers
adding or new vs cutting or sold outSuperinvestors in CSTL
All superinvestors →
Who owns CSTL
share of fund held shares- Index and passive funds32.0%
- Active managers and hedge funds58.9%
- Banks and brokers7.7%
- Pensions, insurers and other1.3%
The top 10 holders own 51.3% of all CSTL shares that funds reported. Groups are our own grouping of filers by name.
Put/call ratio
funds' options, market makers left outAbove 1 means funds hold more puts than calls, a sign of hedging or bets on a fall. Options are valued at the underlying shares.
Filed so far for Q3 2026
66 funds changed their position- AIGH Capital Management LLCSold out−545K sh
- Principal Financial Group IncTrimmed−226K sh
- Mackenzie Financial CorpTrimmed−225K sh
- Dimensional Fund Advisors LPTrimmed−99K sh
- Allspring Global Investments Holdings, LLCTrimmed−48K sh
🔒 Free account: see all 20.
Top holders
Q2 2026| # | Fund | Of company | Shares | Value | Change |
|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | 10.68% | 3.3M | $78.5M | +309K |
| 2 | Rtw Investments, LP | 9.02% | 2.8M | $66.3M | +20K |
| 3 | Principal Financial Group Inc | 5.60% | 1.7M | $41.2M | −43K |
| 4 | Vanguard Capital Management LLC | 3.98% | 1.2M | $29.3M | +49K |
| 5 | Acadian Asset Management LLC | 2.98% | 919K | $21.9M | +434K |
| 6 | Vanguard Portfolio Management LLC | 2.73% | 841K | $20.1M | −21K |
| 7 | Summit Partners Public Asset Management, LLC | 2.68% | 825K | $19.7M | −116K |
| 8 | State Street Corp | 2.67% | 822K | $19.6M | +53K |
| 9 | Allianz Asset Management GmbH | 2.63% | 811K | $19.9M | 0 |
| 10 | Geode Capital Management, LLC | 2.58% | 796K | $19M | +68K |
- Mackenzie Financial Corp+719K sh+$17.2M
- Jefferies Financial Group Inc.+647K sh+$15.4M
- Acadian Asset Management LLC+434K sh+$10.4M
- Point72 Asset Management, L.P.+357K sh+$8.5M
- Kennedy Capital Management LLC+348K sh+$8.3M
- BlackRock, Inc.+309K sh+$7.4M
- First Trust Advisors LP+145K sh+$3.5M
- Citadel Advisors LLC+144K sh+$3.4M
- Portolan Capital Management, LLC−1M sh−$24.4M
- Eventide Asset Management, LLC−386K sh−$9.5M
- Palisade Capital Management, LP−304K sh−$7.2M
- Schroder Investment Management Group−299K sh−$7M
- Nuveen, LLC−290K sh−$6.9M
- SG Americas Securities, LLC−245K sh−$6M
- Dimensional Fund Advisors LP−249K sh−$5.9M
- Tudor Investment Corp ET AL−209K sh−$5M
CSTL institutional ownership FAQ
Who owns the most CSTL stock?
In Q2 2026 13F filings the largest holder of CSTL was BlackRock, Inc., followed by Rtw Investments, LP and Principal Financial Group Inc. Index fund managers are usually the biggest holders of large companies.
What percentage of CSTL is owned by institutions?
Funds that file 13F reports held 88.7% of CSTL's shares at Jun 30, 2026, compared with 89.6% a quarter earlier. That counts every manager with more than $100 million in US stocks.
Are hedge funds buying CSTL?
In Q2 2026, 98 funds bought CSTL (21 of them new positions) and 84 sold (30 sold out completely). Among well known investors, 2 added and 2 cut. Our fund sentiment for CSTL is neutral.
What is CSTL's institutional put/call ratio?
Too few option positions were reported for a meaningful ratio.
How current is this CSTL ownership data?
13F filings show holdings at the end of each quarter and are due within 45 days, so positions can be up to six weeks old when they appear. We add each new filing within minutes, and the "filed so far" list shows funds that have already reported the next quarter.
For informational and educational purposes only. Not investment advice, and not a recommendation to buy or sell any security. Fund sentiment summarises what 13F filings show and is not a forecast. Holdings come from SEC Form 13F filings as reported and show positions at the end of the quarter, up to 45 days before the filing. A 13F leaves out short positions, cash, bonds and most foreign holdings. See all hedge fund holdings.