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William Blair Investment Management

William Blair Investment Management Portfolio holdings

AUM $33.3B
1-Year Est. Return 44.76%
This Fund
S&P 500
This Quarter Est. Return
+3.11%
1 Year Est. Return
+44.76%
3 Year Est. Return
+140.8%
5 Year Est. Return
+166.51%
10 Year Est. Return
+978.6%
AUM
$35.9B
AUM Growth
-$2.82B
Cap. Flow
-$3B
Cap. Flow %
-8.37%
Top 10 Hldgs %
32.55%
Holding
459
New
45
Increased
106
Reduced
259
Closed
46

Top Buys

Rank Stock Value
1
SNOW icon
Snowflake
SNOW
+$202M
2
ARGX icon
argenx
ARGX
+$191M
3
GOOGL icon
Alphabet (Google) Class A
GOOGL
+$191M
4
HQY icon
HealthEquity
HQY
+$178M
5
FFIV icon
F5
FFIV
+$148M

Top Sells

Rank Stock Value
1
LRCX icon
Lam Research
LRCX
+$270M
2
CIEN icon
Ciena
CIEN
+$260M
3
UBER icon
Uber
UBER
+$233M
4
LYV icon
Live Nation Entertainment
LYV
+$229M
5
LRN icon
Stride
LRN
+$225M

Sector Composition

Rank Sector Weight
1 Technology 37.93%
2 Financials 12.94%
3 Healthcare 12.67%
4 Consumer Discretionary 10.8%
5 Industrials 9.43%
Name Market Value Portfolio Weight Shares or Principal Change
in Stake 		Capital Flow
PWP icon
126
Perella Weinberg Partners
PWP
$1.31B
$68.3M 0.19%
3,946,163
+379,652
+11% +$7.09M
AGYS icon
127
Agilysys
AGYS
$3.01B
$68M 0.19%
572,600
+6,378
+1% +$768K
LPX icon
128
Louisiana-Pacific
LPX
$5.17B
$67M 0.19%
829,439
-96,988
-10% -$8.19M
MRX
129
Marex Group Limited Ordinary Shares
MRX
$5.12B
$66.7M 0.19%
1,738,927
+1,370,478
+372% +$46.6M
RVLV icon
130
Revolve Group
RVLV
$1.68B
$64.9M 0.18%
2,148,125
+306,547
+17% +$7.41M
KWR icon
131
Quaker Houghton
KWR
$2.95B
$64.5M 0.18%
469,981
+118,321
+34% +$16M
TME icon
132
Tencent Music
TME
$13.7B
$63M 0.18%
3,592,177
-185,808
-5% -$3.77M
BRBR icon
133
BellRing Brands
BRBR
$1.27B
$59.6M 0.17%
2,228,300
-291,753
-12% -$9.05M
ACGL icon
134
Arch Capital
ACGL
$33.4B
$56.5M 0.16%
588,845
-100,300
-15% -$9.18M
IWF icon
135
iShares Russell 1000 Growth ETF
IWF
$128B
$52.7M 0.15%
445,356
-231,132
-34% -$27.4M
LITE icon
136
Lumentum
LITE
$73.3B
$51.5M 0.14%
139,703
-134,421
-49% -$34.5M
MOD icon
137
Modine Manufacturing
MOD
$10.9B
$51.1M 0.14%
382,915
+1,990
+0.5% +$296K
WSC icon
138
WillScot Mobile Mini Holdings
WSC
$4.09B
$49.9M 0.14%
2,649,427
-2,667,864
-50% -$53.8M
WFRD icon
139
Weatherford International
WFRD
$6.69B
$49.7M 0.14%
635,479
-186,638
-23% -$13.5M
RSI icon
140
Rush Street Interactive
RSI
$2.84B
$49.7M 0.14%
2,557,778
+378,002
+17% +$6.99M
OSIS icon
141
OSI Systems
OSIS
$3.83B
$48.8M 0.14%
+191,326
New +$50M
IBN icon
142
ICICI Bank
IBN
$107B
$47.8M 0.13%
1,605,841
-291,592
-15% -$8.95M
INTR icon
143
Inter&Co
INTR
$2.24B
$47.4M 0.13%
5,595,196
+2,110,861
+61% +$18.7M
TGLS icon
144
Tecnoglass Holdings Inc.
TGLS
$1.87B
$46.8M 0.13%
930,033
-7,430
-0.8% -$406K
ESTA icon
145
Establishment Labs
ESTA
$2.25B
$46.6M 0.13%
639,790
-377,753
-37% -$22.8M
BCPC
146
Balchem Corp
BCPC
$5.72B
$45.9M 0.13%
298,986
+23,511
+9% +$3.59M
ALHC icon
147
Alignment Healthcare
ALHC
$2.79B
$45.5M 0.13%
2,305,255
+185,303
+9% +$3.33M
JLL icon
148
Jones Lang LaSalle
JLL
$16.7B
$45.1M 0.13%
133,953
-9,321
-7% -$2.92M
BANC icon
149
Banc of California
BANC
$3.11B
$44.7M 0.12%
2,317,363
+187,999
+9% +$3.37M
TSEM icon
150
Tower Semiconductor
TSEM
$30.1B
$44.5M 0.12%
378,980
-323,369
-46% -$31.1M
4 5
6
7 8

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William Blair Investment Management's Q4 2025 Portfolio in Review

As of Q4 2025, William Blair Investment Management held 459 positions worth $35.9B, down 7.3% from $38.7B the previous quarter. Its ten largest holdings account for 33% of the portfolio.

William Blair Investment Management withdrew a net $3B in Q4 2025, closing 46 positions and reducing 259 holdings. Its most notable exit was Live Nation Entertainment, an estimated $229M position sold in full.

By sector, the portfolio is most concentrated in Technology at 38% of assets, down from 39% a quarter earlier, followed by Financials and Healthcare.

Against the trend, William Blair Investment Management opened a new position in argenx worth $188M.

  • William Blair Investment Management's largest Q4 2025 buy was argenx: 223,666 shares worth $188M.
  • William Blair Investment Management added most to Snowflake in Q4 2025, an estimated $202M increase.
  • William Blair Investment Management's biggest Q4 2025 reduction was Lam Research, cutting an estimated $270M.
  • William Blair Investment Management fully exited Live Nation Entertainment in Q4 2025, selling an estimated $229M.
  • William Blair Investment Management's ten largest holdings make up 33% of its $35.9B portfolio in Q4 2025.
  • William Blair Investment Management opened 45 new positions and closed 46 in Q4 2025.
  • William Blair Investment Management's portfolio value fell 7.3% quarter-over-quarter to $35.9B.

Based on William Blair Investment Management's 13F filing for Q4 2025, filed 9 Feb 2026.