Ranked by reported Q1 2026 13F market value
Share of total reported institutional value in CSTL held by the largest 10 / 25 filers.
| # | Institution | Shares Held | Market Value | QoQ Change | Ownership % | % of Fund |
|---|---|---|---|---|---|---|
| 1 | BlackRock, Inc. | 3.0M | $73.2M | -3.9% | 9.835% | 0.00% |
| 2 | RTW INVESTMENTS, LP | 2.8M | $67.7M | +30.4% | 9.094% | 0.67% |
| 3 | PRINCIPAL FINANCIAL GROUP INC | 1.8M | $43.5M | -2.1% | 5.835% | 0.02% |
| 4 | Portolan Capital Management, LLC | 1.4M | $33.1M | -21.9% | 4.452% | 1.76% |
| 5 | VANGUARD CAPITAL MANAGEMENT LLC | 1.2M | $28.9M | — | 3.882% | 0.00% |
| 6 | DIMENSIONAL FUND ADVISORS LP | 1.0M | $25.5M | -9.1% | 3.428% | 0.01% |
| 7 | SUMMIT PARTNERS PUBLIC ASSET MANAGEMENT, LLC | 941K | $23.1M | -11.2% | 3.102% | 1.22% |
| 8 | VANGUARD PORTFOLIO MANAGEMENT LLC | 862K | $21.2M | — | 2.841% | 0.00% |
| 9 | Allianz Asset Management GmbH | 811K | $19.9M | +30.4% | 2.675% | 0.02% |
| 10 | STATE STREET CORP | 769K | $18.9M | +4.4% | 2.536% | 0.00% |
| 11 | GEODE CAPITAL MANAGEMENT, LLC | 728K | $17.9M | +1.8% | 2.401% | 0.00% |
| 12 | AIGH Capital Management LLC | 591K | $14.5M | -5.5% | 1.947% | 2.97% |
| 13 | Qube Research & Technologies Ltd | 560K | $13.7M | +137.6% | 1.845% | 0.02% |
| 14 | PALISADE CAPITAL MANAGEMENT LLC/NJ | 536K | $13.2M | -5.6% | 1.767% | 0.44% |
| 15 | RENAISSANCE TECHNOLOGIES LLC | 533K | $13.1M | +8.1% | 1.757% | 0.02% |
| 16 | Nuveen, LLC | 522K | $12.8M | -0.5% | 1.722% | 0.00% |
| 17 | WASATCH ADVISORS INC | 455K | $11.2M | -15.3% | 1.500% | 0.07% |
| 18 | MORGAN STANLEY | 429K | $10.5M | +110.7% | 1.414% | 0.00% |
| 19 | EVENTIDE ASSET MANAGEMENT, LLC | 386K | $9.5M | +26.7% | 1.274% | 0.16% |
| 20 | Connor, Clark & Lunn Investment Management Ltd. | 377K | $9.3M | -2.9% | 1.243% | 0.02% |
| 21 | MILLENNIUM MANAGEMENT LLC | 353K | $8.7M | +14.4% | 1.165% | 0.01% |
| 22 | GOLDMAN SACHS GROUP INC | 341K | $8.4M | +18.8% | 1.125% | 0.00% |
| 23 | SCHRODER INVESTMENT MANAGEMENT GROUP | 299K | $7.0M | -39.3% | 0.986% | 0.01% |
| 24 | NORTHERN TRUST CORP | 273K | $6.7M | +4.1% | 0.900% | 0.00% |
| 25 | SILVERCREST ASSET MANAGEMENT GROUP LLC | 269K | $6.6M | +31.0% | 0.885% | 0.05% |
denotes a marquee investor (Buffett, Burry, ARK, Tiger Global, Pershing Square, Baupost and other widely-followed managers). “% of Fund” shows how much of that investor’s total 13F portfolio is invested in CSTL — a direct measure of their conviction.
Filings activity in CSTL during Q1 2026, grouped by how each filer changed its position.
8 quarters of 13F filings · Δ columns show change vs prior quarter
| Quarter | Inst. Holders | Δ Holders | Ownership % | Δ Ownership | Total 13F Value | Δ Value |
|---|---|---|---|---|---|---|
| Q1 2026 | 183 | 4.7% | 104.03% | 61.85 pp | $653M | 37% |
| Q4 2025 | 192 | +13% | 165.88% | +71.86 pp | $1.04B | +76% |
| Q3 2025 | 170 | +11% | 94.02% | +11.46 pp | $590M | +14% |
| Q2 2025 | 153 | 15% | 82.56% | +5.65 pp | $518M | +7.3% |
| Q1 2025 | 179 | 6.8% | 76.91% | 23.63 pp | $483M | 23% |
| Q4 2024 | 192 | +6.1% | 100.54% | 7.14 pp | $631M | 6.6% |
| Q3 2024 | 181 | +16% | 107.68% | +26.19 pp | $676M | +32% |
| Q2 2024 | 156 | — | 81.49% | — | $512M | — |
Source: SEC 13F institutional filings. Ownership % requires market cap data and will show once linked. Δ columns compare to the immediately prior filed quarter.
Quick answers to the most common questions about buying CSTL stock.
Based on Q1 2026 13F filings, institutional ownership of Castle Biosciences, Inc. stands at 104.0%, held across 183 reporting institutions.
BlackRock, Inc. is the largest reported institutional holder of CSTL, with approximately 2,982,946 shares worth $0.07B as of Q1 2026.
Yes — 2 widely-followed marquee investors appear among the top 25 institutional holders of CSTL, including RENAISSANCE TECHNOLOGIES LLC, MILLENNIUM MANAGEMENT LLC.
Our composite Smart Money Score for CSTL is 39 out of 100 (Bearish). It combines net institutional buying activity, ownership shift, marquee investor presence, and holder-count growth.
30 institutions opened new positions in CSTL during Q1 2026, while 39 fully exited. 32 added to existing positions and 120 trimmed.
CSTL institutional ownership fell by 61.85 percentage points quarter-over-quarter, with a net change of -9 holders.
The top 10 institutions account for 54.4% of all reported 13F value in CSTL, and the top 25 account for 79.3%.
All data is sourced from SEC Form 13F filings, which institutional investment managers with at least $100M in assets are required to file each quarter. We process every 13F filing from EDGAR and recompute the aggregates after each cycle. Insider transactions are sourced from Form 4 filings.
Castle Biosciences, Inc. (CSTL) Institutional Ownership