WESTFIELD CAPITAL MANAGEMENT CO LP

CIK

1177719

Location

BOSTON, MA

Portfolio Value

Large $23,803,945,248

Diversification

Diversified

Filing Date

Global Rank

#244 / 8,603 ▲ 5 · as of Mar 2026

Top Industry

Biotechnology 10.4%

3Y Alpha vs SPY

-1.4%

Period ended 3 months ago

Filed May 11, 2026 · 59d

25 quarters · since Mar 2020

Clone Performance

Jul 2023–Jul 2026 · vs SPY

Hypothetical growth of cloning every reported 13F position and rebalancing on each filing, indexed to the same start.

Cloned portfolio

+68.2%

SPY

+76.0%

Annualised alpha

-1.8%

Max drawdown

−25.8%

Estimate. 13F holdings are quarter-lagged and long-only, so the clone rebalances about 45 days after each period end — when the filing becomes public — and excludes options and short positions. Past performance does not predict future results.

Portfolio Concentration

243 positions · as of Mar 31, 2026 · Δ vs Dec 31, 2025

Top Position

4.6%

−0.0 pts

Top 5

19.1%

−0.1 pts

Top 10

30.4%

+0.5 pts

HHI

142

Diversified+2

Portfolio Trend

25 quarters · across all stocks

Sector Breakdown

As of Mar 31, 2026

Sector	% Portfolio	Value	Positions
Technology	28.5%	$6,775,203,452	58
Industrials	25.3%	$6,011,674,358	43
Healthcare	15.8%	$3,766,470,562	49
Consumer Cyclical	10.5%	$2,501,827,195	27
Financial Services	8.9%	$2,111,651,462	32
Communication Services	5.9%	$1,399,076,589	8
Energy	2.7%	$642,147,704	10
Consumer Defensive	0.9%	$217,580,314	6
Basic Materials	0.6%	$144,486,926	4
Utilities	0.5%	$127,757,381	4
Real Estate	0.4%	$106,069,305	2

Last Quarter's Activity

Export CSV

Mar 31, 2026 vs Dec 31, 2025

Added To

Positions the filer increased

25 positions

Ticker	Company	Δ Shares	Shares	Value
CELH	Celsius Holdings, Inc.	+2,224,696	3,768,911	$133,720,962
BRZE	Braze, Inc.	+1,786,631	3,973,906	$93,823,920
PR	Permian Resources Corp	+1,530,271	7,481,457	$159,504,663
ADPT	Adaptive Biotechnologies Corp	+1,376,237	5,436,718	$75,461,645
APG	APi Group Corp	+1,181,574	4,634,929	$187,807,323
KEY	Keycorp /New/	+1,153,037	5,193,334	$104,126,346
IOT	Samsara Inc.	+1,118,851	5,072,821	$160,757,697
INSM	INSMED Inc	+1,035,938	1,468,459	$240,122,415
RGTI	Rigetti Computing, Inc.	+959,535	1,895,313	$26,610,194
DT	Dynatrace, Inc.	+852,886	4,209,594	$155,670,786
GH	Guardant Health, Inc.	+823,349	1,362,539	$125,857,727
ALAB	Astera Labs, Inc.	+664,819	860,113	$94,268,384
RYTM	Rhythm Pharmaceuticals, Inc.	+661,965	1,929,123	$167,775,827
RKLB	Rocket Lab Corp	+580,168	3,172,611	$203,745,078
BROS	Dutch Bros Inc.	+533,741	2,313,357	$117,194,665
TOST	Toast, Inc.	+522,536	1,790,873	$47,476,043
PLTR	Palantir Technologies Inc.	+519,972	674,557	$98,674,197
FTAI	FTAI Aviation Ltd.	+497,602	2,848,227	$697,815,615
CRDO	Credo Technology Group Holding Ltd	+455,532	926,219	$86,944,177
ARES	Ares Management Corp	+421,587	1,572,787	$171,591,061
CALX	Calix, Inc	+400,809	1,546,101	$75,743,487
STEP	StepStone Group Inc.	+391,470	1,177,971	$56,212,776
BIRK	Birkenstock Holding plc	+383,978	2,338,779	$83,798,451
PLXS	Plexus Corp	+379,293	384,493	$77,875,212
NFLX	Netflix Inc	+372,447	1,969,994	$189,414,923
No positions match the current search.

Trimmed

Positions the filer reduced

25 positions

Ticker	Company	Δ Shares	Shares	Value
GENI	Genius Sports Ltd	−5,744,053	207,150	$917,674
BAC	Bank Of America Corp /De/	−2,756,724	1,066,885	$52,010,643
OPCH	Option Care Health, Inc.	−1,582,491	1,182,814	$31,841,352
DXCM	Dexcom Inc	−1,412,615	27,074	$1,700,247
FITB	Fifth Third Bancorp	−1,361,504	2,385,422	$110,826,706
RVMD	Revolution Medicines, Inc.	−1,288,435	1,556,578	$151,377,210
HQY	Healthequity, Inc.	−1,239,604	712,848	$59,572,707
MASI	Masimo Corp	−1,180,820	341,229	$60,694,402
SMTC	Semtech Corp	−1,168,018	1,280,594	$98,464,872
CWST	Casella Waste Systems Inc	−842,734	822,492	$65,256,515
APLD	Applied Digital Corp.	−492,305	542,092	$12,869,264
ABBV	AbbVie Inc.	−409,165	10,619	$2,309,526
LEGN	Legend Biotech Corp	−401,202	5,763,475	$104,261,262
DSGX	Descartes Systems Group Inc	−391,967	801,902	$57,384,107
PODD	Insulet Corp	−384,786	1,682	$352,950
ASND	Ascendis Pharma A/S	−372,256	4,813,440	$1,100,978,131
VRT	Vertiv Holdings Co	−356,020	1,921,696	$481,538,583
RMBS	Rambus Inc	−347,656	14,436	$1,241,929
WCN	Waste Connections, Inc.	−308,810	4,466	$725,457
MRVL	Marvell Technology, Inc.	−274,426	1,673,381	$165,748,388
COHR	Coherent Corp.	−268,479	396,644	$94,484,567
AMD	Advanced Micro Devices Inc	−245,435	5,020	$1,021,218
UNH	Unitedhealth Group Inc	−227,511	2,767	$748,722
RRX	Regal Rexnord Corp	−211,383	681,717	$127,658,325
DHR	Danaher Corp /De/	−210,995	110,492	$20,949,283
No positions match the current search.

New Positions

Positions the filer opened this quarter

25 positions

Ticker	Company	Shares	Value
LNG	Cheniere Energy, Inc.	459,044	$130,258,325
AS	Amer Sports, Inc.	3,937,521	$129,623,191
AIG	American International Group, Inc.	1,458,711	$109,768,002
JLL	Jones Lang Lasalle Inc	347,779	$105,836,105
ROST	Ross Stores, Inc.	471,916	$102,231,163
WWD	Woodward, Inc.	272,185	$97,420,455
ANET	Arista Networks, Inc.	780,402	$95,817,757
LTH	Life Time Group Holdings, Inc.	3,185,515	$85,817,774
MS	Morgan Stanley	496,558	$81,718,550
MTZ	Mastec Inc	249,980	$80,428,565
GWRE	Guidewire Software, Inc.	486,581	$72,773,054
LOW	Lowes Companies Inc	300,962	$71,111,301
NAMS	NewAmsterdam Pharma Co N.V.	2,202,913	$70,515,245
MCHP	Microchip Technology Inc	970,295	$62,690,759
IBP	Installed Building Products, Inc.	208,248	$55,216,957
GKOS	GLAUKOS Corp	482,219	$51,915,697
CDE	Coeur Mining, Inc.	2,738,846	$51,408,139
MAR	Marriott International Inc /Md/	153,219	$50,113,338
MDGL	Madrigal Pharmaceuticals, Inc.	94,813	$49,631,761
NXPI	NXP Semiconductors N.V.	247,996	$48,820,492
PL	Planet Labs PBC	1,637,041	$45,755,295
ENTG	Entegris Inc	371,686	$43,576,466
RIOT	Riot Platforms, Inc.	3,499,880	$43,258,516
CPAY	Corpay, Inc.	143,120	$41,646,488
MU	Micron Technology Inc	100,434	$33,930,622
No positions match the current search.

Sold Out

Positions the filer fully exited

25 positions

Ticker	Company	Shares	Value
CVLT	Commvault Systems Inc	1,057,077	$132,515,172
TEAM	Atlassian Corp	812,215	$131,692,540
ADMA	Adma Biologics, Inc.	6,992,907	$127,550,623
ALKT	Alkami Technology, Inc.	4,118,355	$95,010,449
ORCL	Oracle Corp	474,397	$92,464,719
BURL	Burlington Stores, Inc.	302,307	$87,321,376
DKNG	DraftKings Inc.	2,383,054	$82,120,040
TRU	TransUnion	933,553	$80,052,169
VMC	Vulcan Materials CO	254,044	$72,458,429
SLAB	Silicon Laboratories Inc.	547,403	$71,545,572
AJG	Arthur J. Gallagher & Co.	259,491	$67,153,675
OWL	Blue Owl Capital Inc.	4,423,608	$66,088,703
PRI	Primerica, Inc.	234,597	$60,610,480
IRTC	iRhythm Holdings, Inc.	325,063	$57,679,178
BIO	Bio-Rad Laboratories, Inc.	165,107	$50,025,769
FNB	Fnb Corp/Pa/	2,903,113	$49,643,232
BLDR	Builders FirstSource, Inc.	475,697	$48,944,464
RYAN	Ryan Specialty Holdings, Inc.	814,334	$42,044,064
NIQ	NIQ Global Intelligence plc	2,388,660	$39,389,003
RBLX	Roblox Corp	461,670	$37,409,120
FORM	Formfactor Inc	449,604	$25,078,911
BCYC	Bicycle Therapeutics PLC	3,016,026	$21,353,464
CTAS	Cintas Corp	42,271	$7,949,906
CME	Cme Group Inc.	21,785	$5,949,047
SLB	Slb Limited/Nv	120,910	$4,640,525
No positions match the current search.

Portfolio Positions

Compact Export CSV View 13F filing

243 positions · $23,803,945,248 total · as of Mar 31, 2026

All sectors Basic Materials Communication Services Consumer Cyclical Consumer Defensive Energy Financial Services Healthcare Industrials Real Estate Technology Utilities

Showing 1–50 of 243 positions by value · page 1 of 5

Ticker	Company	Type	Shares	Δ Shares	Value (USD)	% Δ Value	% of Portfolio
NVDA	Nvidia Corp Technology	Added	6,317,039	+365,990	$1,101,691,601	−0.7%	4.63%
ASND	Ascendis Pharma A/S Healthcare	Reduced	4,813,440	-372,256	$1,100,978,131	−0.4%	4.63%
FIX	Comfort Systems USA Inc Industrials	Reduced	620,915	-47,920	$856,235,575	+37.2%	3.60%
AAPL	Apple Inc. Technology	Reduced	3,133,113	-141,205	$795,152,748	−10.7%	3.34%
FTAI	FTAI Aviation Ltd. Industrials	Added	2,848,227	+497,602	$697,815,615	+50.8%	2.93%
MSFT	Microsoft Corp Technology	Added	1,649,513	+28,294	$610,600,227	−22.1%	2.57%
GOOGL	Alphabet Inc. Communication Services	Reduced	2,026,744	-151,734	$582,810,504	−14.5%	2.45%
HWM	Howmet Aerospace Inc. Industrials	Added	2,289,697	+70,572	$527,683,570	+16.0%	2.22%
VRT	Vertiv Holdings Co Industrials	Reduced	1,921,696	-356,020	$481,538,583	+30.5%	2.02%
AMZN	Amazon Com Inc Consumer Cyclical	Reduced	2,279,654	-51,116	$474,783,538	−11.7%	1.99%
AXON	Axon Enterprise, Inc. Industrials	Added	1,064,134	+232,957	$451,927,068	−4.3%	1.90%
AVGO	Broadcom Inc. Technology	Added	1,236,925	+124,607	$382,840,656	−0.6%	1.61%
LLY	ELI LILLY & Co Healthcare	Added	364,579	+87,030	$335,328,826	+12.4%	1.41%
TPR	Tapestry, Inc. Consumer Cyclical	Added	2,198,862	+100,758	$310,281,416	+15.7%	1.30%
META	Meta Platforms, Inc. Communication Services	Reduced	526,822	-128,461	$301,410,670	−30.3%	1.27%
LPLA	LPL Financial Holdings Inc. Financial Services	Added	881,506	+255,944	$265,183,449	+18.7%	1.11%
MKSI	Mks Inc Technology	Added	1,046,763	+206,990	$240,556,605	+79.3%	1.01%
INSM	INSMED Inc Healthcare	Added	1,468,459	+1,035,938	$240,122,415	+219.0%	1.01%
PCVX	Vaxcyte, Inc. Healthcare	Added	3,646,138	+106,421	$211,877,079	+29.7%	0.89%
RKLB	Rocket Lab Corp Industrials	Added	3,172,611	+580,168	$203,745,078	+12.7%	0.86%
NFLX	Netflix Inc Communication Services	Added	1,969,994	+372,447	$189,414,923	+26.5%	0.80%
APG	APi Group Corp Industrials	Added	4,634,929	+1,181,574	$187,807,323	+42.1%	0.79%
PWR	Quanta Services, Inc. Industrials	Added	331,816	+58,288	$182,173,620	+57.8%	0.77%
GEV	GE Vernova Inc. Industrials	Added	199,306	+21,372	$173,974,207	+49.6%	0.73%
ARES	Ares Management Corp Financial Services	Added	1,572,787	+421,587	$171,591,061	−7.8%	0.72%
RYTM	Rhythm Pharmaceuticals, Inc. Healthcare	Added	1,929,123	+661,965	$167,775,827	+23.7%	0.70%
TSM	Taiwan Semiconductor Manufacturing Co Ltd Technology	Added	493,504	+47,309	$166,779,676	+23.0%	0.70%
MRVL	Marvell Technology, Inc. Technology	Reduced	1,673,381	-274,426	$165,748,388	+0.1%	0.70%
BE	Bloom Energy Corp Industrials	Added	1,191,572	+46,276	$161,446,090	+62.2%	0.68%
IOT	Samsara Inc. Technology	Added	5,072,821	+1,118,851	$160,757,697	+14.7%	0.68%
AME	Ametek Inc/ Industrials	Reduced	745,832	-154,384	$159,876,547	−13.5%	0.67%
PR	Permian Resources Corp Energy	Added	7,481,457	+1,530,271	$159,504,663	+91.0%	0.67%
DT	Dynatrace, Inc. Technology	Added	4,209,594	+852,886	$155,670,786	+7.0%	0.65%
RVMD	Revolution Medicines, Inc. Healthcare	Reduced	1,556,578	-1,288,435	$151,377,210	−33.2%	0.64%
NTRA	Natera, Inc. Healthcare	Added	754,729	+40,037	$150,938,252	−7.8%	0.63%
FN	Fabrinet Technology	Added	284,874	+94,704	$148,567,488	+71.6%	0.62%
ABVX	Abivax S.A. Healthcare	Added	1,322,938	+312,972	$147,309,146	+8.2%	0.62%
NOW	ServiceNow, Inc. Technology	Reduced	1,394,187	-82,616	$145,762,250	−35.6%	0.61%
FTI	TechnipFMC plc Energy	Added	2,033,755	+81,328	$140,593,483	+61.6%	0.59%
RCL	Royal Caribbean Cruises Ltd Consumer Cyclical	Added	505,765	+57,112	$139,176,412	+11.2%	0.58%
HLT	Hilton Worldwide Holdings Inc. Consumer Cyclical	Added	457,425	+99,704	$139,093,794	+35.4%	0.58%
V	Visa Inc. Financial Services	Reduced	456,548	-147,378	$137,987,067	−34.9%	0.58%
COR	Cencora, Inc. Healthcare	Added	436,909	+117,694	$137,250,593	+27.3%	0.58%
ITT	Itt Inc. Industrials	Added	703,309	+115,863	$134,001,463	+31.5%	0.56%
CELH	Celsius Holdings, Inc. Consumer Defensive	Added	3,768,911	+2,224,696	$133,720,962	+89.3%	0.56%
NXT	Nextpower Inc. Technology	Added	1,107,346	+17,046	$133,490,560	+40.6%	0.56%
LNG	Cheniere Energy, Inc. Energy	NEW	459,044	NEW	$130,258,325	NEW	0.55%
AS	Amer Sports, Inc. Consumer Cyclical	NEW	3,937,521	NEW	$129,623,191	NEW	0.54%
RRX	Regal Rexnord Corp Industrials	Reduced	681,717	-211,383	$127,658,325	+1.9%	0.54%
MSCI	MSCI Inc. Financial Services	Added	233,764	+25,972	$126,001,133	+5.7%	0.53%