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William Blair & Company

William Blair & Company Portfolio holdings

AUM $34.9B
1-Year Est. Return 18.88%
This Fund
S&P 500
This Quarter Est. Return
+1.73%
1 Year Est. Return
+18.88%
3 Year Est. Return
+73.84%
5 Year Est. Return
+90.13%
10 Year Est. Return
+563.35%
AUM
$37.3B
AUM Growth
-$310M
Cap. Flow
-$212M
Cap. Flow %
-0.57%
Top 10 Hldgs %
27.41%
Holding
1,963
New
120
Increased
759
Reduced
753
Closed
96

Top Buys

Rank Stock Value
1
BWXT icon
BWX Technologies
BWXT
+$46.6M
2
META icon
Meta Platforms (Facebook)
META
+$38.3M
3
NOW icon
ServiceNow
NOW
+$37.6M
4
VEU icon
Vanguard FTSE All-World ex-US ETF
VEU
+$32.4M
5
GLD icon
SPDR Gold Trust
GLD
+$29.4M

Top Sells

Rank Stock Value
1
FISV
Fiserv Inc
FISV
+$114M
2
CSGP icon
CoStar Group
CSGP
+$78.3M
3
CWAN
Clearwater Analytics
CWAN
+$75.3M
4
POOL icon
Pool Corp
POOL
+$54M
5
ZTS icon
Zoetis
ZTS
+$51.3M

Sector Composition

Rank Sector Weight
1 Technology 25.8%
2 Financials 13.4%
3 Industrials 12.04%
4 Healthcare 11.22%
5 Communication Services 7.63%
Name Market Value Portfolio Weight Shares or Principal Change
in Stake 		Capital Flow
IESC icon
1901
IES Holdings
IESC
$15.2B
– –
-525
Closed -$209K
IMCV icon
1902
iShares Morningstar Mid-Cap Value ETF
IMCV
$1.16B
– –
-1,944
Closed -$156K
IPAC icon
1903
iShares Core MSCI Pacific ETF
IPAC
$2.77B
– –
-139
Closed -$10.2K
K
1904
DELISTED
Kellanova
K
– –
-8,961
Closed -$735K
KRRO icon
1905
Korro Bio
KRRO
$195M
– –
-9,750
Closed -$467K
MZTI
1906
The Marzetti Company
MZTI
$3.11B
– –
-1,913
Closed -$331K
LGLV icon
1907
State Street SPDR US Large Cap Low Volatility Index ETF
LGLV
$1.23B
– –
-147
Closed -$26.2K
LLYVA icon
1908
Liberty Live Group Series A
LLYVA
$9.09B
– –
-169
Closed -$15.9K
LLYVK icon
1909
Liberty Live Group Series C
LLYVK
$9.46B
– –
-795
Closed -$77.1K
LNW
1910
DELISTED
Light & Wonder
LNW
– –
-20,296
Closed -$1.7M
LPX icon
1911
Louisiana-Pacific
LPX
$5.49B
– –
-2,312
Closed -$205K
LYG icon
1912
Lloyds Banking Group
LYG
$91.3B
– –
-13,154
Closed -$59.7K
MBLY icon
1913
Mobileye
MBLY
$2.2B
– –
-10,533
Closed -$149K
MKTX icon
1914
MarketAxess Holdings
MKTX
$5.72B
– –
-1,687
Closed -$294K
DFTX
1915
Definium Therapeutics
DFTX
$6.12B
– –
-31,905
Closed -$376K
MRC
1916
DELISTED
MRC Global
MRC
– –
-19,512
Closed -$281K
MRUS
1917
DELISTED
Merus
MRUS
– –
-2,151
Closed -$203K
MTDR icon
1918
Matador Resources
MTDR
$6.09B
– –
-11,359
Closed -$510K
MXI icon
1919
iShares Global Materials ETF
MXI
$362M
– –
-100
Closed -$9.25K
MYRG icon
1920
MYR Group
MYRG
$5.25B
– –
-2,031
Closed -$423K
NICE icon
1921
Nice
NICE
$5.97B
– –
-1,742
Closed -$252K
OLED icon
1922
Universal Display
OLED
$4.19B
– –
-2,482
Closed -$356K
ON icon
1923
ON Semiconductor
ON
$31.6B
– –
-5,763
Closed -$284K
PSR icon
1924
Invesco Active US Real Estate Fund
PSR
$60M
– –
-4
Closed -$371
REZ icon
1925
iShares Residential and Multisector Real Estate ETF
REZ
$874M
– –
-151
Closed -$12.8K
75 76
77
78 79

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William Blair & Company's Q4 2025 Portfolio in Review

As of Q4 2025, William Blair & Company held 1,963 positions worth $37.3B, down 0.82% from $37.6B the previous quarter. Its ten largest holdings account for 27% of the portfolio.

William Blair & Company's Q4 2025 filing shows 120 new, 759 increased, 753 reduced and 96 closed positions. Its largest new stake was Wingstop: 90,773 shares worth $21.6M. The largest sale was Fiserv Inc, an estimated $114M.

By sector, the portfolio is most concentrated in Technology at 26% of assets, down from 27% a quarter earlier, followed by Financials and Industrials.

  • William Blair & Company's largest Q4 2025 buy was Wingstop: 90,773 shares worth $21.6M.
  • William Blair & Company added most to BWX Technologies in Q4 2025, an estimated $46.6M increase.
  • William Blair & Company's biggest Q4 2025 reduction was Fiserv Inc, cutting an estimated $114M.
  • William Blair & Company fully exited SAP in Q4 2025, selling an estimated $9.19M.
  • William Blair & Company's ten largest holdings make up 27% of its $37.3B portfolio in Q4 2025.
  • William Blair & Company opened 120 new positions and closed 96 in Q4 2025.
  • William Blair & Company's portfolio value fell 0.82% quarter-over-quarter to $37.3B.

Based on William Blair & Company's 13F filing for Q4 2025, filed 17 Feb 2026.