Castle Biosciences Ownership | Who Owns Castle Biosciences?

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Castle Biosciences Ownership Summary

Castle Biosciences is owned by 91.76% institutional investors, 3.16% insiders, and 5.08% retail investors. Blackrock is the largest institutional shareholder, holding 11.08% of CSTL shares. Bellevue Healthcare Ord is the top mutual fund, with 4.32% of its assets in Castle Biosciences shares.

CSTL Ownership Benchmark

Type	Name	% Inst	% Insiders	% Retail
Stock	Castle Biosciences	91.76%	3.16%	5.08%
Sector	Healthcare Stocks	487.91%	11.08%	-398.99%
Industry	Diagnostics & Research Stocks	57.29%	10.84%	31.88%

Institutional Shareholders

Top Institutional Shareholders by Total Shares

Holder	Shares	% Holding	Value
Blackrock	3.04M	11.08%	$66.29M
Blackrock funding, inc. /de	3.15M	10.91%	$64.42M
Vanguard group	1.83M	6.58%	$48.84M
Principal financial group	1.44M	5.16%	$38.26M
Portolan capital management	1.49M	5.15%	$30.42M
Wasatch advisors lp	1.05M	3.63%	$21.44M
Dimensional fund advisors lp	999.47K	3.59%	$26.64M
Ubs group	812.60K	2.92%	$21.66M
Braidwell lp	822.74K	2.85%	$16.80M
Wellington management group llp	722.12K	2.59%	$19.24M

Top Institutional Shareholders by % of Total Assets

Holder	Shares	% Assets	Value
Birchview capital, lp	110.60K	2.24%	$2.26M
Portolan capital management	1.49M	1.91%	$30.42M
Parkman healthcare partners	352.26K	0.83%	$7.19M
Perkins capital management	28.00K	0.57%	$571.66K
Braidwell lp	822.74K	0.57%	$16.80M
Palisade capital management, lp	575.12K	0.33%	$11.74M
Green alpha advisors	9.54K	0.21%	$217.18K
Alpha dna investment management	15.17K	0.15%	$404.39K
Kornitzer capital management inc /ks	278.31K	0.11%	$5.68M
Wasatch advisors lp	1.05M	0.11%	$21.44M

Top Buyers

Holder	Shares	% Assets	Change
Ubs group	812.60K	0.00%	758.47K
Wellington management group llp	722.12K	0.00%	722.12K
Braidwell lp	822.74K	0.57%	457.49K
Blackrock	3.04M	0.00%	449.29K
Millennium management	548.81K	0.01%	408.27K

Top Sellers

Holder	Shares	% Assets	Change
Park west asset management	-	-	-556.49K
Morgan stanley	249.38K	0.00%	-401.33K
Bellevue group	-	-	-301.10K
Soleus capital management	-	-	-252.92K
Cubist systematic strategies	-	-	-237.70K

New Positions

Holder	Shares	% Assets	Change	Value
Wellington management group llp	722.12K	0.00%	722.12K	$19.24M
Bnp paribas arbitrage, snc	249.13K	0.00%	249.13K	$6.64M
D. e. shaw	90.56K	0.00%	90.56K	$2.41M
Empowered funds	40.75K	0.01%	40.75K	$832.12K
Aqr capital management	21.11K	0.00%	21.11K	$562.72K

Sold Out

Holder	Change
National bank of canada /fi/	-1.00
Nelson, van denburg & campbell wealth management group	-1.00
Stephens consulting	-2.00
Colonial trust advisors	-6.00
Larson financial group	-12.00

Institutional Ownership Trends

Date	Holdings	Change %	Shares	Change %	Ownership	Change %	Increased Position	Change %	Decreased Position	Change %
Jun 30, 2025	151	-17.03%	26,530,454	2.55%	91	1.12%	85	-19.81%	44	-18.52%
Mar 31, 2025	178	-13.17%	25,557,223	-3.26%	89	0.99%	105	-2.78%	53	-19.70%
Dec 31, 2024	202	3.59%	26,322,033	2.20%	94	1.10%	106	-11.67%	65	38.30%
Sep 30, 2024	195	18.90%	25,754,395	2.29%	92	1.12%	119	38.37%	48	-4.00%
Jun 30, 2024	163	7.24%	25,178,603	0.98%	91	1.08%	85	18.06%	50	-7.41%

Top Mutual Funds Shareholders

Holder	Shares	% Holding	Change
Bellevue Healthcare Ord	1.20M	4.32%	1.20M
Vanguard US Total Market Shares ETF	829.40K	2.96%	-
Principal SmallCap R5	829.94K	2.86%	78.59K
Vanguard Total Stock Mkt Idx Inv	826.46K	2.85%	-18.32K
Principal U.S. Small Cap Equity	781.42K	2.71%	159.12K
Strategic Advisers U.S. Total Stock{mg}	693.06K	2.47%	-
Wasatch Small Cap Growth Investor	675.19K	2.41%	-14.34K
Strategic Advisers Small-Mid Cap	665.91K	2.40%	62.85K
iShares Russell 2000 ETF	691.79K	2.38%	-
Wasatch Ultra Growth	627.21K	2.17%	33.31K

Recent Insider Transactions

Date	Name	Role	Activity	Value
Oct 20, 2025	MAETZOLD DEREK J	Pres. & Chief Exec. Officer	Sell	$30.05K
Oct 02, 2025	MAETZOLD DEREK J	Pres. & Chief Exec. Officer	Sell	$30.23K
Sep 17, 2025	MAETZOLD DEREK J	Pres. & Chief Exec. Officer	Sell	$29.42K
Sep 02, 2025	MAETZOLD DEREK J	Pres. & Chief Exec. Officer	Sell	$32.04K
Aug 27, 2025	Oelschlager Kristen M	Chief Operating Officer	Sell	$279.13K

Insider Transactions Trends

Date	Buy	Sell
2025 Q3	-	6
2025 Q2	-	20
2025 Q1	-	61
2024 Q4	-	64
2024 Q3	-	55

CSTL Ownership FAQ

Who Owns Castle Biosciences?

Castle Biosciences shareholders are primarily institutional investors at 91.76%, followed by 3.16% insiders and 5.08% retail investors. The average institutional ownership in Castle Biosciences's industry, Diagnostics & Research Stocks, is 57.29%, which Castle Biosciences exceeds.

Who owns the most shares of Castle Biosciences?

Castle Biosciences’s largest shareholders are Blackrock (3.04M shares, 11.08%), Blackrock funding, inc. /de (3.15M shares, 10.91%), and Vanguard group (1.83M shares, 6.58%). Together, they hold 28.57% of Castle Biosciences’s total shares outstanding.

Does Blackrock own Castle Biosciences?

Yes, BlackRock owns 11.08% of Castle Biosciences, totaling 3.04M shares as of Jun 2024. This represents 0.00% of BlackRock's total assets, with a market value of 66.29M$. In the last quarter, BlackRock increased its holdings by 449.29K shares, a 17.31% change.

Who is Castle Biosciences’s biggest shareholder by percentage of total assets invested?

Birchview capital, lp is Castle Biosciences’s biggest shareholder by percentage of total assets invested, with 2.24% of its assets in 110.6K Castle Biosciences shares, valued at 2.26M$.

Who is the top mutual fund holder of Castle Biosciences shares?

Bellevue Healthcare Ord is the top mutual fund holder of Castle Biosciences shares, with 4.32% of its total shares outstanding invested in 1.2M Castle Biosciences shares.

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