WESTFIELD CAPITAL MANAGEMENT CO LP

CIK

1177719

Location

BOSTON, MA

Portfolio Value

Large $23,810,970,015

Diversification

Diversified

Filing Date

Global Rank

#157 / 8,232 ▲ 94

Top Industry

Biotechnology 10.4%

3Y Alpha vs SPY

-1.9%

Period ended 2 months ago

Filed May 11, 2026 · 34d

24 quarters · since Mar 2020

Clone Performance

Jun 2023–Jun 2026 · vs SPY

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

Cloned portfolio

+68.8%

SPY

+76.3%

Annualised alpha

-1.7%

Max drawdown

−25.7%

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 Sep 30, 2025

Top Position

4.6%

−0.6 pts

Top 5

19.1%

−1.2 pts

Top 10

30.4%

−1.2 pts

HHI

142

Diversified−9

Portfolio Trend

24 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%	$6,018,658,027	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%	$144,528,024	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 Sep 30, 2025

Added To

Positions the filer increased

25 positions

Ticker	Company	Δ Shares	Shares	Value
PR	Permian Resources Corp	+4,123,741	7,481,457	$159,504,663
RIOT	Riot Platforms, Inc.	+2,149,853	3,499,880	$43,258,516
BRZE	Braze, Inc.	+1,795,953	3,973,906	$93,823,920
NFLX	Netflix Inc	+1,739,346	1,969,994	$189,414,923
IOT	Samsara Inc.	+1,271,034	5,072,821	$160,757,697
NOW	ServiceNow, Inc.	+1,134,185	1,394,187	$145,762,250
IONQ	IonQ, Inc.	+1,006,121	1,373,788	$39,606,308
INSM	INSMED Inc	+980,532	1,468,459	$240,122,415
DT	Dynatrace, Inc.	+863,814	4,209,594	$155,670,786
CALX	Calix, Inc	+862,005	1,546,101	$75,743,487
RYTM	Rhythm Pharmaceuticals, Inc.	+860,119	1,929,123	$167,775,827
WGS	GeneDx Holdings Corp.	+825,014	1,369,108	$87,924,115
FITB	Fifth Third Bancorp	+765,474	2,385,422	$110,826,706
TOST	Toast, Inc.	+756,568	1,790,873	$47,476,043
RKLB	Rocket Lab Corp	+734,791	3,172,611	$203,745,078
MKSI	Mks Inc	+723,399	1,046,763	$240,556,605
FTAI	FTAI Aviation Ltd.	+717,986	2,848,227	$697,815,615
IMAX	Imax Corp	+716,151	2,338,776	$88,896,875
KEY	Keycorp /New/	+713,120	5,193,334	$104,126,346
ALAB	Astera Labs, Inc.	+667,499	860,113	$94,268,384
KTOS	Kratos Defense & Security Solutions, Inc.	+557,330	1,563,146	$110,217,424
FTI	TechnipFMC plc	+553,645	2,033,755	$140,593,483
ARES	Ares Management Corp	+545,198	1,572,787	$171,591,061
CRDO	Credo Technology Group Holding Ltd	+453,378	926,219	$86,944,177
GL	Globe Life Inc.	+411,781	842,423	$117,240,008
No positions match the current search.

Trimmed

Positions the filer reduced

25 positions

Ticker	Company	Δ Shares	Shares	Value
GENI	Genius Sports Ltd	−5,642,933	207,150	$917,674
BAC	Bank Of America Corp /De/	−2,794,218	1,066,885	$52,010,643
DXCM	Dexcom Inc	−2,285,136	27,074	$1,700,247
SMTC	Semtech Corp	−2,099,779	1,280,594	$98,464,872
OPCH	Option Care Health, Inc.	−1,575,044	1,182,814	$31,841,352
MASI	Masimo Corp	−1,078,021	341,229	$60,694,402
COHR	Coherent Corp.	−1,076,319	396,644	$94,484,567
HQY	Healthequity, Inc.	−1,003,810	712,848	$59,572,707
RVMD	Revolution Medicines, Inc.	−957,389	1,556,578	$151,377,210
MRVL	Marvell Technology, Inc.	−938,577	1,673,381	$165,748,388
CWST	Casella Waste Systems Inc	−825,415	822,492	$65,256,515
GKOS	GLAUKOS Corp	−749,422	482,219	$51,915,697
MNDY	monday.com Ltd.	−679,949	13,370	$924,000
RRX	Regal Rexnord Corp	−540,013	681,717	$127,658,325
PCOR	Procore Technologies, Inc.	−539,012	1,001,253	$57,071,421
CORZ	Core Scientific, Inc./tx	−512,722	1,480,013	$22,140,994
SN	SharkNinja, Inc.	−497,756	904,541	$95,790,891
BE	Bloom Energy Corp	−483,710	1,191,572	$161,446,090
RMBS	Rambus Inc	−470,029	14,436	$1,241,929
KRMN	Karman Holdings Inc.	−461,271	964,305	$77,192,615
ASND	Ascendis Pharma A/S	−446,469	4,813,440	$1,100,978,131
LEGN	Legend Biotech Corp	−331,011	5,763,475	$104,261,262
VRT	Vertiv Holdings Co	−325,522	1,921,696	$481,538,583
MTSI	MACOM Technology Solutions Holdings, Inc.	−304,039	132,457	$29,414,725
NXT	Nextpower Inc.	−290,711	1,107,346	$133,490,560
No positions match the current search.

New Positions

Positions the filer opened this quarter

25 positions

Ticker	Company	Shares	Value
APG	APi Group Corp	4,634,929	$187,807,323
ABVX	Abivax S.A.	1,322,938	$147,309,146
CELH	Celsius Holdings, Inc.	3,768,911	$133,720,962
LNG	Cheniere Energy, Inc.	459,044	$130,258,325
AS	Amer Sports, Inc.	3,937,521	$129,623,191
GH	Guardant Health, Inc.	1,362,539	$125,857,727
BROS	Dutch Bros Inc.	2,313,357	$117,194,665
AIG	American International Group, Inc.	1,458,711	$109,768,002
JLL	Jones Lang Lasalle Inc	347,779	$105,836,105
LGN	Legence Corp.	1,861,653	$105,108,928
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
GRMN	Garmin Ltd	376,362	$87,319,747
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
ADPT	Adaptive Biotechnologies Corp	5,436,718	$75,461,645
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
PKG	Packaging Corp Of America	303,771	$64,466,281
MCHP	Microchip Technology Inc	970,295	$62,690,759
ZS	Zscaler, Inc.	427,919	$60,032,756
IBP	Installed Building Products, Inc.	208,248	$55,216,957
No positions match the current search.

Sold Out

Positions the filer fully exited

25 positions

Ticker	Company	Shares	Value
ORCL	Oracle Corp	600,197	$168,799,404
RBLX	Roblox Corp	1,189,575	$164,779,929
CVLT	Commvault Systems Inc	786,175	$148,414,116
IP	International Paper Co /New/	2,341,336	$108,637,990
TRU	TransUnion	1,180,154	$98,873,302
COST	Costco Wholesale Corp /New	92,163	$85,308,837
AJG	Arthur J. Gallagher & Co.	267,709	$82,920,185
DKNG	DraftKings Inc.	2,080,438	$77,808,381
ALKT	Alkami Technology, Inc.	3,095,058	$76,881,240
ADMA	Adma Biologics, Inc.	5,106,802	$74,865,717
BLDR	Builders FirstSource, Inc.	616,032	$74,693,880
VMC	Vulcan Materials CO	236,556	$72,769,356
RYAN	Ryan Specialty Holdings, Inc.	1,278,134	$72,035,632
OWL	Blue Owl Capital Inc.	4,228,444	$71,587,556
PRI	Primerica, Inc.	256,774	$71,277,894
PRCT	PROCEPT BioRobotics Corp	1,970,147	$70,314,546
ICLR	Icon PLC	396,354	$69,361,950
RH	Rh	332,901	$67,632,167
PINS	Pinterest, Inc.	2,023,270	$65,088,595
VEEV	Veeva Systems Inc	217,754	$64,871,094
ICE	Intercontinental Exchange, Inc.	378,565	$63,780,631
SLNO	Soleno Therapeutics Inc	899,157	$60,783,013
KNSL	Kinsale Capital Group, Inc.	142,146	$60,449,007
TWLO	Twilio Inc	591,367	$59,189,923
SPOT	Spotify Technology S.A.	84,006	$58,636,188
No positions match the current search.

Portfolio Positions

Compact Export CSV View 13F filing

243 positions · $23,810,970,015 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	Reduced	6,317,039	-190,126	$1,101,691,601	−9.3%	4.63%
ASND	Ascendis Pharma A/S Healthcare	Reduced	4,813,440	-446,469	$1,100,978,131	+5.3%	4.62%
FIX	Comfort Systems USA Inc Industrials	Reduced	620,915	-212,280	$856,235,575	+24.5%	3.60%
AAPL	Apple Inc. Technology	Reduced	3,133,113	-201,432	$795,152,748	−6.4%	3.34%
FTAI	FTAI Aviation Ltd. Industrials	Added	2,848,227	+717,986	$697,815,615	+96.3%	2.93%
MSFT	Microsoft Corp Technology	Reduced	1,649,513	-55,723	$610,600,227	−30.9%	2.56%
GOOGL	Alphabet Inc. Communication Services	Reduced	2,026,744	-217,906	$582,810,504	+6.8%	2.45%
HWM	Howmet Aerospace Inc. Industrials	Added	2,289,697	+282,244	$527,683,570	+34.0%	2.22%
VRT	Vertiv Holdings Co Industrials	Reduced	1,921,696	-325,522	$481,538,583	+42.0%	2.02%
AMZN	Amazon Com Inc Consumer Cyclical	Reduced	2,279,654	-262,075	$474,783,538	−14.9%	1.99%
AXON	Axon Enterprise, Inc. Industrials	Added	1,064,134	+334,982	$451,927,068	−13.6%	1.90%
AVGO	Broadcom Inc. Technology	Added	1,236,925	+70,563	$382,840,656	−0.5%	1.61%
LLY	ELI LILLY & Co Healthcare	Added	364,579	+87,574	$335,328,826	+58.7%	1.41%
TPR	Tapestry, Inc. Consumer Cyclical	Reduced	2,198,862	-251,809	$310,281,416	+11.8%	1.30%
META	Meta Platforms, Inc. Communication Services	Reduced	526,822	-240,835	$301,410,670	−46.5%	1.27%
LPLA	LPL Financial Holdings Inc. Financial Services	Added	881,506	+306,044	$265,183,449	+38.5%	1.11%
MKSI	Mks Inc Technology	Added	1,046,763	+723,399	$240,556,605	+501.0%	1.01%
INSM	INSMED Inc Healthcare	Added	1,468,459	+980,532	$240,122,415	+241.7%	1.01%
PCVX	Vaxcyte, Inc. Healthcare	Reduced	3,646,138	-86,577	$211,877,079	+57.6%	0.89%
RKLB	Rocket Lab Corp Industrials	Added	3,172,611	+734,791	$203,745,078	+74.4%	0.86%
NFLX	Netflix Inc Communication Services	Added	1,969,994	+1,739,346	$189,414,923	+585.0%	0.80%
APG	APi Group Corp Industrials	NEW	4,634,929	NEW	$187,807,323	NEW	0.79%
PWR	Quanta Services, Inc. Industrials	Added	331,816	+86,310	$182,173,620	+79.1%	0.77%
GEV	GE Vernova Inc. Industrials	Reduced	199,306	-66,430	$173,974,207	+6.5%	0.73%
ARES	Ares Management Corp Financial Services	Added	1,572,787	+545,198	$171,591,061	+4.4%	0.72%
RYTM	Rhythm Pharmaceuticals, Inc. Healthcare	Added	1,929,123	+860,119	$167,775,827	+55.4%	0.70%
TSM	Taiwan Semiconductor Manufacturing Co Ltd Technology	Added	493,504	+26,106	$166,779,676	+27.8%	0.70%
MRVL	Marvell Technology, Inc. Technology	Reduced	1,673,381	-938,577	$165,748,388	−24.5%	0.70%
BE	Bloom Energy Corp Industrials	Reduced	1,191,572	-483,710	$161,446,090	+14.0%	0.68%
IOT	Samsara Inc. Technology	Added	5,072,821	+1,271,034	$160,757,697	+13.5%	0.68%
AME	Ametek Inc/ Industrials	Added	745,832	+387,172	$159,876,547	+137.1%	0.67%
PR	Permian Resources Corp Energy	Added	7,481,457	+4,123,741	$159,504,663	+271.1%	0.67%
DT	Dynatrace, Inc. Technology	Added	4,209,594	+863,814	$155,670,786	−4.0%	0.65%
RVMD	Revolution Medicines, Inc. Healthcare	Reduced	1,556,578	-957,389	$151,377,210	+28.9%	0.64%
NTRA	Natera, Inc. Healthcare	Added	754,729	+178,927	$150,938,252	+62.8%	0.63%
FN	Fabrinet Technology	Added	284,874	+121,872	$148,567,488	+150.0%	0.62%
ABVX	Abivax S.A. Healthcare	NEW	1,322,938	NEW	$147,309,146	NEW	0.62%
NOW	ServiceNow, Inc. Technology	Added	1,394,187	+1,134,185	$145,762,250	+204.6%	0.61%
FTI	TechnipFMC plc Energy	Added	2,033,755	+553,645	$140,593,483	+140.8%	0.59%
RCL	Royal Caribbean Cruises Ltd Consumer Cyclical	Added	505,765	+169,253	$139,176,412	+27.8%	0.58%
HLT	Hilton Worldwide Holdings Inc. Consumer Cyclical	Added	457,425	+223,707	$139,093,794	+129.4%	0.58%
V	Visa Inc. Financial Services	Reduced	456,548	-249,219	$137,987,067	−42.7%	0.58%
COR	Cencora, Inc. Healthcare	Added	436,909	+111,249	$137,250,593	+34.9%	0.58%
ITT	Itt Inc. Industrials	Added	703,309	+135,282	$134,001,463	+32.0%	0.56%
CELH	Celsius Holdings, Inc. Consumer Defensive	NEW	3,768,911	NEW	$133,720,962	NEW	0.56%
NXT	Nextpower Inc. Technology	Reduced	1,107,346	-290,711	$133,490,560	+29.0%	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	-540,013	$127,658,325	−27.2%	0.54%
MSCI	MSCI Inc. Financial Services	Added	233,764	+58,417	$126,001,133	+26.6%	0.53%