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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
+7.16%
1 Year Est. Return
+18.88%
3 Year Est. Return
+73.84%
5 Year Est. Return
+90.13%
10 Year Est. Return
+512.03%
AUM
$37.6B
AUM Growth
+$1.57B
Cap. Flow
-$160M
Cap. Flow %
-0.43%
Top 10 Hldgs %
26.02%
Holding
1,919
New
98
Increased
697
Reduced
774
Closed
75

Top Buys

Rank Stock Value
1
META icon
Meta Platforms (Facebook)
META
+$76.1M
2
APP icon
Applovin
APP
+$75.3M
3
NOW icon
ServiceNow
NOW
+$66.6M
4
CWAN
Clearwater Analytics
CWAN
+$65.8M
5
FANG icon
Diamondback Energy
FANG
+$30.7M

Top Sells

Rank Stock Value
1
CYBR
CyberArk
CYBR
+$70.7M
2
ADBE icon
Adobe
ADBE
+$61.7M
3
MSFT icon
Microsoft
MSFT
+$45.7M
4
WDAY icon
Workday
WDAY
+$42.6M
5
POOL icon
Pool Corp
POOL
+$41.7M

Sector Composition

Rank Sector Weight
1 Technology 27.36%
2 Financials 13.36%
3 Industrials 12.59%
4 Healthcare 10.97%
5 Consumer Discretionary 7.45%
Name Market Value Portfolio Weight Shares or Principal Change
in Stake 		Capital Flow
MSFT icon
1
Microsoft
MSFT
$2.93T
$1.87B 4.97%
3,607,106
-89,598
-2% -$45.7M
AAPL icon
2
Apple
AAPL
$4.99T
$1.53B 4.06%
5,992,795
-34,085
-0.6% -$7.7M
AMZN icon
3
Amazon
AMZN
$2.45T
$1.32B 3.51%
6,006,885
-114,990
-2% -$26M
NVDA icon
4
NVIDIA
NVDA
$4.67T
$1.05B 2.8%
5,645,112
+45,974
+0.8% +$8.01M
GOOG icon
5
Alphabet (Google) Class C
GOOG
$4.07T
$766M 2.04%
3,145,955
-34,074
-1% -$7.16M
JPM icon
6
JPMorgan Chase
JPM
$931B
$728M 1.94%
2,306,918
-22,827
-1% -$6.79M
V icon
7
Visa
V
$707B
$670M 1.78%
1,962,153
-108,900
-5% -$37.7M
IDXX icon
8
Idexx Laboratories
IDXX
$44.9B
$659M 1.75%
1,031,786
-48,719
-5% -$29.6M
GOOGL icon
9
Alphabet (Google) Class A
GOOGL
$4.09T
$614M 1.63%
2,525,974
+838
+0% +$176K
SPY icon
10
State Street SPDR S&P 500 ETF Trust
SPY
$777B
$572M 1.52%
859,344
-321
-0% -$206K
MA icon
11
Mastercard
MA
$501B
$555M 1.48%
976,597
-30,726
-3% -$17.6M
COST icon
12
Costco
COST
$431B
$511M 1.36%
551,558
-428
-0.1% -$410K
META icon
13
Meta Platforms (Facebook)
META
$1.5T
$499M 1.33%
678,857
+102,259
+18% +$76.1M
UBER icon
14
Uber
UBER
$143B
$416M 1.11%
4,247,493
-76,540
-2% -$7.16M
GEV icon
15
GE Vernova
GEV
$244B
$386M 1.03%
628,121
-4,685
-0.7% -$2.84M
VEEV icon
16
Veeva Systems
VEEV
$33.8B
$384M 1.02%
1,289,252
+4,290
+0.3% +$1.21M
NOW icon
17
ServiceNow
NOW
$118B
$367M 0.98%
1,995,405
+356,465
+22% +$66.6M
PGR icon
18
Progressive
PGR
$129B
$355M 0.95%
1,439,156
-66,265
-4% -$16.3M
FAST icon
19
Fastenal
FAST
$54.4B
$342M 0.91%
6,965,564
+142,591
+2% +$6.74M
APH icon
20
Amphenol
APH
$189B
$340M 0.91%
2,751,514
-219,934
-7% -$24.1M
SYK icon
21
Stryker
SYK
$134B
$340M 0.9%
919,505
-4,752
-0.5% -$1.84M
WSO icon
22
Watsco Inc
WSO
$12.9B
$323M 0.86%
799,956
-6,700
-0.8% -$2.86M
HD icon
23
Home Depot
HD
$339B
$310M 0.83%
765,895
+6,535
+0.9% +$2.57M
IVV icon
24
iShares Core S&P 500 ETF
IVV
$864B
$299M 0.8%
446,312
+10,169
+2% +$6.55M
AVGO icon
25
Broadcom
AVGO
$1.78T
$294M 0.78%
889,716
-44,731
-5% -$13.7M
1
2 3 4 5

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William Blair & Company's Q3 2025 Portfolio in Review

As of Q3 2025, William Blair & Company held 1,919 positions worth $37.6B, up 4.4% from $36B the previous quarter. Its ten largest holdings account for 26% of the portfolio.

William Blair & Company's Q3 2025 filing shows 98 new, 697 increased, 774 reduced and 75 closed positions. Its largest new stake was Miami International Holdings: 363,765 shares worth $14.6M. The largest sale was CyberArk, an estimated $70.7M.

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

  • William Blair & Company's largest Q3 2025 buy was Miami International Holdings: 363,765 shares worth $14.6M.
  • William Blair & Company added most to Meta Platforms (Facebook) in Q3 2025, an estimated $76.1M increase.
  • William Blair & Company's biggest Q3 2025 reduction was CyberArk, cutting an estimated $70.7M.
  • William Blair & Company fully exited Stride in Q3 2025, selling an estimated $7.47M.
  • William Blair & Company's ten largest holdings make up 26% of its $37.6B portfolio in Q3 2025.
  • William Blair & Company opened 98 new positions and closed 75 in Q3 2025.
  • William Blair & Company's portfolio value rose 4.4% quarter-over-quarter to $37.6B.

Based on William Blair & Company's 13F filing for Q3 2025, filed 12 Nov 2025.