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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
MSFT icon
1
Microsoft
MSFT
$3.71T
$1.73B 4.64%
3,574,568
-32,538
-0.9% -$16.3M
AAPL icon
2
Apple
AAPL
$4.57T
$1.62B 4.34%
5,949,948
-42,847
-0.7% -$11.5M
AMZN icon
3
Amazon
AMZN
$2.96T
$1.4B 3.76%
6,064,424
+57,539
+1% +$13.2M
NVDA icon
4
NVIDIA
NVDA
$5.42T
$1.02B 2.75%
5,494,350
-150,762
-3% -$28.1M
GOOG icon
5
Alphabet (Google) Class C
GOOG
$4.32T
$979M 2.63%
3,118,759
-27,196
-0.9% -$7.79M
GOOGL icon
6
Alphabet (Google) Class A
GOOGL
$4.33T
$780M 2.09%
2,493,580
-32,394
-1% -$9.26M
JPM icon
7
JPMorgan Chase
JPM
$950B
$744M 2%
2,309,809
+2,891
+0.1% +$895K
IDXX icon
8
Idexx Laboratories
IDXX
$46.2B
$677M 1.82%
1,001,375
-30,411
-3% -$20.7M
V icon
9
Visa
V
$677B
$677M 1.82%
1,929,237
-32,916
-2% -$11.2M
SPY icon
10
State Street SPDR S&P 500 ETF Trust
SPY
$823B
$585M 1.57%
857,803
-1,541
-0.2% -$1.04M
MA icon
11
Mastercard
MA
$493B
$545M 1.46%
955,188
-21,409
-2% -$12M
META icon
12
Meta Platforms (Facebook)
META
$1.51T
$486M 1.3%
736,202
+57,345
+8% +$38.3M
COST icon
13
Costco
COST
$420B
$449M 1.21%
521,182
-30,376
-6% -$27.5M
GEV icon
14
GE Vernova
GEV
$264B
$426M 1.14%
652,306
+24,185
+4% +$14.7M
APH icon
15
Amphenol
APH
$209B
$359M 0.96%
2,653,891
-97,623
-4% -$13.1M
LLY icon
16
Eli Lilly
LLY
$1.06T
$349M 0.94%
324,796
+25,247
+8% +$24.1M
NOW icon
17
ServiceNow
NOW
$129B
$339M 0.91%
2,214,840
+219,435
+11% +$37.6M
UBER icon
18
Uber
UBER
$153B
$336M 0.9%
4,107,558
-139,935
-3% -$12.6M
IVV icon
19
iShares Core S&P 500 ETF
IVV
$902B
$335M 0.9%
488,420
+42,108
+9% +$28.6M
PGR icon
20
Progressive
PGR
$125B
$320M 0.86%
1,407,032
-32,124
-2% -$7.25M
DHR icon
21
Danaher
DHR
$144B
$314M 0.84%
1,372,624
+6,522
+0.5% +$1.43M
AVGO icon
22
Broadcom
AVGO
$2.04T
$310M 0.83%
896,446
+6,730
+0.8% +$2.41M
ABBV icon
23
AbbVie
ABBV
$435B
$306M 0.82%
1,337,461
+73,880
+6% +$16.8M
SYK icon
24
Stryker
SYK
$130B
$297M 0.8%
844,899
-74,606
-8% -$27.2M
FAST icon
25
Fastenal
FAST
$59.5B
$281M 0.76%
7,014,666
+49,102
+0.7% +$2.07M
1
2 3 4 5

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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.