WESTFIELD CAPITAL MANAGEMENT CO LP

Registered adviser

CIK

1177719

Location

BOSTON, MA

Portfolio Value

Large $30,614,525,829

Diversification

Diversified

Filing Date

Global Rank

#269 / 8,818 ▲ 9

Top Industry

Semiconductors 12.7%

Period ended 4 months ago

Filed Aug 12, 2026 · 3mo

26 quarters · since Mar 2020

Regulatory profile

From Form ADV, the SEC filer profile, 13D/13G type codes and N-CEN, never from the name.

Holder type

Registered adviser

Form ADV roster, Oct 1, 2026

Form ADV adviser

CRD 146990

Roster of Oct 1, 2026

Regulatory AUM

$29,807,982,355

Main clients

Diversified

Private funds

2 funds · Mixed

Focus by fund count, roster of Oct 1, 2026

$71,269,342 gross assets

Private funds on Schedule D 7.B.(1)

As filed Sep 10, 2024; SEC's bulk Form ADV archive ends with 2024 filings.

$57,295,948 gross assets in 3 funds Hedge funds $32,452,328 (1) Other private funds $24,843,620 (2)

Form ADV history

Monthly rosters from Dec 2019; each row is a run with the same figures, newest first.

Rosters	Regulatory AUM	Main clients
Aug 2026 to Oct 2026	$29,807,982,355	Diversified
Apr 2026 to Jul 2026	$24,404,194,926	Diversified
Apr 2025 to Mar 2026	$23,551,448,142	Diversified
Apr 2024 to Mar 2025	$17,556,838,117	Diversified
Aug 2023 to Mar 2024	$13,315,528,816	Diversified
May 2023 to Jul 2023	$13,315,528,816	Diversified

5 earlier changes not shown.

Portfolio style

Measured from the filed 13F common-share book for Jun 30, 2026, never from the firm's own description.

Style

Diversified active

Top 10 weight 29.3%, 72.3 effective positions, active share 67.2% against the Russell 1000 as of 2026-06-30; it meets none of the index-like, systematic-like or concentrated tests

Turnover

Medium turnover

67.6% over the last four quarters (30% to under 100%)

Horizon

Horizon unknown

The value-weighted holding period is at least 11.7 quarters, but 25.9% of the book was already held when coverage starts

Closest benchmark: the Russell 1000 as of 2026-06-30, active share 67.2%; sector active share 26.2% against the combined 13F book's sector weights.

Over time 26 measured quarters

How the bands are measured

Style bands measure the filed 13F common-share book each closed quarter, tested in this order. Unknown: under $10,000,000 of valued equity or 5 stocks. Index-like (100+ stocks): active share of 20% or less against the closest benchmark, which is the S&P 500, S&P MidCap 400, S&P SmallCap 600, Russell 1000, Russell 2000, Nasdaq-100 or Dow Jones Industrial Average (weighted by an index-tracking fund's reported holdings or the index's constituents nearest the quarter end, over the names resolved to companies, and only when those are 90%+ of its weight) or every 13F filer's combined book, or index series holding 80%+ of the registered fund assets it advises (N-CEN) and equal to 50%+ of its book. Systematic-like: 500+ stocks, 100%+ annual turnover and a top 10 weight of 25% or less. Concentrated: a top 10 weight of 60%+ or 12 or fewer effective positions. Diversified active: none of these. Turnover is the smaller of buys and sells over average equity value, summed over four quarters: low under 30%, high 100%+. Horizon is the value-weighted number of quarters each position has been held: short under 4, long 12+.

Clone Performance

Build a hypothetical price-return history from this filer's public 13F holdings.

View clone backtest

Portfolio Concentration

278 tracked positions · as of Jun 30, 2026 · Δ vs Mar 31, 2026

Top Position

5.3%

+0.7 pts

Top 5

19.2%

+0.1 pts

Top 10

29.3%

−1.1 pts

HHI

138

Diversified−4

Portfolio Trend

26 quarters · across all stocks

Sector Breakdown

As of Jun 30, 2026

Sector	% Portfolio	Value	Positions
Technology	33.3%	$10,196,714,736	72
Industrials	24.0%	$7,351,490,462	50
Healthcare	16.4%	$5,013,745,716	53
Financial Services	7.6%	$2,326,645,781	30
Consumer Cyclical	7.3%	$2,248,591,309	27
Communication Services	7.1%	$2,179,639,687	9
Energy	1.6%	$488,964,732	11
Consumer Defensive	1.1%	$335,442,714	7
Basic Materials	0.6%	$176,904,376	5
Real Estate	0.5%	$156,796,888	4
Utilities	0.4%	$133,864,785	4
Unclassified	0.0%	$5,724,643	6

Last Quarter's Activity

Export CSV

Jun 30, 2026 vs Mar 31, 2026

Added To

Positions the filer increased

25 positions

Ticker	Company	Δ Shares	Shares	Value
LTH	Life Time Group Holdings, Inc.	+2,809,739	5,995,254	$244,846,173
AS	Amer Sports, Inc.	+2,407,402	6,344,923	$214,712,194
PL	Planet Labs PBC	+1,790,966	3,428,007	$113,569,871
NVDA	Nvidia Corp	+1,762,887	8,079,926	$1,616,712,393
GOOGL	Alphabet Inc.	+1,722,330	3,749,074	$1,339,806,575
CELH	Celsius Holdings, Inc.	+1,555,570	5,324,481	$155,900,803
APG	APi Group Corp	+1,519,372	6,154,301	$260,634,647
CSX	Csx Corp	+1,496,120	3,154,419	$149,929,535
KEY	Keycorp	+1,300,133	6,493,467	$149,674,414
GILD	Gilead Sciences, Inc.	+1,260,939	1,287,629	$162,679,047
UEC	Uranium Energy Corp	+1,232,973	2,800,745	$29,855,941
SNOW	Snowflake Inc.	+1,017,688	1,736,498	$441,938,741
NOW	ServiceNow, Inc.	+979,524	2,373,711	$235,662,028
CORZ	Core Scientific, Inc.	+929,881	2,409,894	$61,669,187
IOT	Samsara Inc.	+763,638	5,836,459	$189,276,365
MCHP	Microchip Technology Inc	+668,816	1,639,111	$149,486,923
C	Citigroup Inc	+563,667	608,124	$85,113,035
STEP	StepStone Group Inc.	+551,453	1,729,424	$71,528,976
ANET	Arista Networks, Inc.	+536,694	1,317,096	$223,748,268
APLD	Applied Digital Corp.	+497,549	1,039,641	$38,778,609
GRMN	Garmin Ltd	+484,695	861,057	$204,535,479
PTRN	Pattern Group Inc.	+483,278	1,656,169	$41,718,897
MS	Morgan Stanley	+444,002	940,560	$196,614,662
RDNT	RadNet, Inc.	+443,649	975,542	$60,161,675
AXON	Axon Enterprise, Inc.	+427,356	1,491,490	$836,144,208
No positions match the current search.

Trimmed

Positions the filer reduced

25 positions

Ticker	Company	Δ Shares	Shares	Value
RIOT	Riot Platforms, Inc.	−2,486,076	1,013,804	$27,757,953
PR	Permian Resources Corp	−1,724,569	5,756,888	$105,984,308
NFLX	Netflix Inc	−1,679,161	290,833	$20,765,476
FITB	Fifth Third Bancorp	−1,674,407	711,015	$40,079,915
MRVL	Marvell Technology, Inc.	−1,660,188	13,193	$3,930,062
AMZN	Amazon Com Inc	−1,419,848	859,806	$204,926,162
BRZE	Braze, Inc.	−1,356,374	2,617,532	$56,774,269
LEGN	Legend Biotech Corp	−1,333,412	4,430,063	$127,940,219
BE	Bloom Energy Corp	−1,181,002	10,570	$3,199,539
PCVX	Vaxcyte, Inc.	−1,173,710	2,472,428	$143,722,239
ADPT	Adaptive Biotechnologies Corp	−1,169,073	4,267,645	$91,540,985
RKLB	Rocket Lab Corp	−1,058,606	2,114,005	$214,888,608
RVMD	Revolution Medicines, Inc.	−955,757	600,821	$112,521,756
KRMN	Karman Holdings Inc.	−929,505	34,800	$1,737,216
VRT	Vertiv Holdings Co	−867,335	1,054,361	$353,021,150
BAC	Bank Of America Corp	−826,698	240,187	$13,685,855
CRDO	Credo Technology Group Holding Ltd	−709,243	216,976	$59,006,623
NAMS	NewAmsterdam Pharma Co N.V.	−666,441	1,536,472	$52,071,036
ARES	Ares Management Corp	−620,755	952,032	$105,970,681
ALAB	Astera Labs, Inc.	−610,814	249,299	$120,416,402
AAPL	Apple Inc.	−559,339	2,573,774	$744,747,244
LGN	Legence Corp.	−519,690	1,341,963	$114,375,506
TPR	Tapestry, Inc.	−502,293	1,696,569	$248,343,770
ROKU	Roku, Inc	−461,662	716,557	$98,985,183
TOST	Toast, Inc.	−417,652	1,373,221	$38,203,008
No positions match the current search.

New Positions

Positions the filer opened this quarter

25 positions

Ticker	Company	Shares	Value
CRS	Carpenter Technology Corp	314,082	$193,738,340
PTCT	Ptc Therapeutics, Inc.	1,956,156	$159,563,644
LRCX	Lam Research Corp	285,614	$123,765,114
ASML	Asml Holding NV	57,430	$114,253,533
SNDK	Sandisk Corp	49,024	$111,467,339
NPO	Enpro Inc.	286,554	$108,010,799
FROG	JFrog Ltd	1,114,561	$101,291,303
TTMI	Ttm Technologies Inc	416,052	$77,810,045
FPS	Forgent Power Solutions, Inc.	1,370,928	$76,580,038
RBRK	Rubrik, Inc.	937,308	$75,247,086
SFM	Sprouts Farmers Market, Inc.	866,638	$73,300,242
—		585,583	$72,319,501
DY	Dycom Industries Inc	141,978	$71,782,657
TER	Teradyne, Inc	136,491	$66,039,805
ST	Sensata Technologies Holding plc	1,333,853	$63,678,142
BTSG	BrightSpring Health Services, Inc.	897,804	$62,612,850
RLAY	Relay Therapeutics, Inc.	3,343,496	$62,556,810
BLDR	Builders FirstSource, Inc.	656,421	$58,736,551
RBLX	Roblox Corp	985,802	$53,607,912
ARGX	Argenx SE	57,082	$52,958,967
FLEX	Flex Ltd.	314,008	$50,891,276
SPOT	Spotify Technology S.A.	110,179	$50,586,484
ADI	Analog Devices Inc	126,445	$50,220,160
NDAQ	Nasdaq, Inc.	635,713	$50,106,898
STX	Seagate Technology Holdings plc	50,734	$48,958,310
No positions match the current search.

Sold Out

Positions the filer fully exited

25 positions

Ticker	Company	Shares	Value
KTOS	Kratos Defense & Security Solutions, Inc.	1,563,146	$110,217,424
AIG	American International Group, Inc.	1,458,711	$109,768,002
PLTR	Palantir Technologies Inc.	674,557	$98,674,197
WGS	GeneDx Holdings Corp.	1,369,108	$87,924,115
FFIV	F5, Inc.	298,542	$86,377,156
CHRW	C. H. Robinson Worldwide, Inc.	429,500	$71,327,065
LOW	Lowes Companies Inc	300,962	$71,111,301
—		341,229	$60,694,349
ZS	Zscaler, Inc.	427,919	$60,032,756
HUBS	Hubspot Inc	232,976	$56,869,441
IBP	Installed Building Products, Inc.	208,248	$55,216,957
MCO	Moodys Corp	123,603	$53,921,808
—		148,581	$52,196,505
KKR	KKR & Co. Inc.	558,136	$51,627,580
TECH	BIO-TECHNE Corp	856,043	$44,736,807
FICO	Fair Isaac Corp	39,934	$42,631,142
IONQ	IonQ, Inc.	1,373,788	$39,606,308
HLNE	Hamilton Lane INC	364,174	$36,198,895
OPCH	Option Care Health, Inc.	1,182,814	$31,841,352
TDG	TransDigm Group INC	12,950	$15,008,532
WFC	Wells Fargo & Company	87,713	$6,982,831
MTB	M&T Bank Corp	29,839	$6,168,318
RJF	Raymond James Financial Inc	40,095	$5,805,355
MCD	Mcdonalds Corp	18,034	$5,604,786
MDT	Medtronic plc	60,349	$5,229,240
No positions match the current search.

Portfolio Positions

Compact Export CSV View 13F filing

278 tracked positions · $30,614,525,829 total · filing declares 278 positions · $30,614,527,190 · as of Jun 30, 2026

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

Showing 1–50 of 278 positions by value · page 1 of 6

Ticker	Company	Type	Shares	Δ Shares	Value (USD)	% Δ Value	Held (qtrs)	Est. cost/share	% of Portfolio
NVDA	Nvidia Corp Technology	Added	8,079,926	+1,762,887	$1,616,712,393	+46.7%	26+	before history	5.28%
GOOGL	Alphabet Inc. Communication Services	Added	3,749,074	+1,722,330	$1,339,806,575	+129.9%	26+	before history	4.38%
ASND	Ascendis Pharma A/S Healthcare	Reduced	4,798,267	-15,173	$1,279,793,774	+16.2%	26+	before history	4.18%
AXON	Axon Enterprise, Inc. Industrials	Added	1,491,490	+427,356	$836,144,208	+85.0%	15	$401.42	2.73%
FTAI	FTAI Aviation Ltd. Industrials	Added	2,937,228	+89,001	$794,608,290	+13.9%	9	$149.10	2.60%
AAPL	Apple Inc. Technology	Reduced	2,573,774	-559,339	$744,747,244	−6.3%	26+	before history	2.43%
FIX	Comfort Systems USA Inc Industrials	Reduced	355,433	-265,482	$704,450,434	−17.7%	11	$284.29	2.30%
AVGO	Broadcom Inc. Technology	Added	1,556,522	+319,597	$587,976,185	+53.6%	26+	before history	1.92%
MSFT	Microsoft Corp Technology	Reduced	1,414,294	-235,219	$527,559,947	−13.6%	26+	before history	1.72%
HWM	Howmet Aerospace Inc. Industrials	Reduced	1,921,476	-368,221	$516,608,037	−2.1%	6	$148.30	1.69%
LLY	ELI LILLY & Co Healthcare	Added	416,732	+52,153	$499,840,904	+49.1%	17	$858.76	1.63%
SNOW	Snowflake Inc. Technology	Added	1,736,498	+1,017,688	$441,938,741	+307.7%	5	$189.49	1.44%
MKSI	Mks Inc Technology	Reduced	928,617	-118,146	$413,048,841	+71.7%	4	$150.82	1.35%
META	Meta Platforms, Inc. Communication Services	Added	677,389	+150,567	$381,566,449	+26.6%	14	$348.53	1.25%
VRT	Vertiv Holdings Co Industrials	Reduced	1,054,361	-867,335	$353,021,150	−26.7%	12	$58.70	1.15%
GEV	GE Vernova Inc. Industrials	Added	241,272	+41,966	$283,460,821	+62.9%	8	$417.12	0.93%
MU	Micron Technology Inc Technology	Added	228,203	+127,769	$263,412,440	+676.3%	2	$592.26	0.86%
V	Visa Inc. Financial Services	Added	762,403	+305,855	$261,572,845	+89.6%	26+	before history	0.85%
APG	APi Group Corp Industrials	Added	6,154,301	+1,519,372	$260,634,647	+38.8%	3	$39.67	0.85%
TPR	Tapestry, Inc. Consumer Cyclical	Reduced	1,696,569	-502,293	$248,343,770	−20.0%	22	$52.49	0.81%
RYTM	Rhythm Pharmaceuticals, Inc. Healthcare	Added	2,208,595	+279,472	$245,220,302	+46.2%	6	$77.45	0.80%
LTH	Life Time Group Holdings, Inc. Consumer Cyclical	Added	5,995,254	+2,809,739	$244,846,173	+185.3%	2	$29.57	0.80%
TSM	Taiwan Semiconductor Manufacturing Co Ltd Technology	Added	510,999	+17,495	$244,037,792	+46.3%	10	$158.86	0.80%
GH	Guardant Health, Inc. Healthcare	Added	1,624,459	+261,920	$243,717,583	+93.6%	3	$98.12	0.80%
PWR	Quanta Services, Inc. Industrials	Reduced	331,489	-327	$238,685,339	+31.0%	5	$380.47	0.78%
NOW	ServiceNow, Inc. Technology	Added	2,373,711	+979,524	$235,662,028	+61.7%	26+	before history	0.77%
AMD	Advanced Micro Devices Inc Technology	Added	403,081	+398,061	$234,153,783	+22828.9%	3	$407.68	0.76%
PANW	Palo Alto Networks Inc Technology	Added	658,331	+21,848	$224,504,037	+120.0%	4	$187.20	0.73%
WWD	Woodward, Inc. Industrials	Added	526,505	+254,320	$223,996,287	+129.9%	2	$369.34	0.73%
ANET	Arista Networks, Inc. Technology	Added	1,317,096	+536,694	$223,748,268	+133.5%	2	$143.27	0.73%
LPLA	LPL Financial Holdings Inc. Financial Services	Reduced	793,061	-88,445	$223,389,422	−15.8%	26+	before history	0.73%
RKLB	Rocket Lab Corp Industrials	Reduced	2,114,005	-1,058,606	$214,888,608	+5.5%	5	$35.87	0.70%
AS	Amer Sports, Inc. Consumer Cyclical	Added	6,344,923	+2,407,402	$214,712,194	+65.6%	2	$35.96	0.70%
NET	Cloudflare, Inc. Technology	Added	835,502	+293,936	$204,931,930	+83.4%	5	$177.61	0.67%
AMZN	Amazon Com Inc Consumer Cyclical	Reduced	859,806	-1,419,848	$204,926,162	−56.8%	26+	before history	0.67%
GRMN	Garmin Ltd Technology	Added	861,057	+484,695	$204,535,479	+134.2%	3	$232.24	0.67%
RRX	Regal Rexnord Corp Industrials	Added	856,976	+175,259	$204,123,113	+59.9%	11	$161.73	0.67%
NTRA	Natera, Inc. Healthcare	Reduced	726,628	-28,101	$197,243,170	+30.7%	7	$163.52	0.64%
MS	Morgan Stanley Financial Services	Added	940,560	+444,002	$196,614,662	+140.6%	2	$184.88	0.64%
CRS	Carpenter Technology Corp Industrials	NEW	314,082	NEW	$193,738,340	NEW	1	$470.82	0.63%
IOT	Samsara Inc. Technology	Added	5,836,459	+763,638	$189,276,365	+17.7%	19	unpriced	0.62%
DT	Dynatrace, Inc. Technology	Added	4,249,229	+39,635	$186,583,645	+19.9%	15	$44.73	0.61%
CAT	Caterpillar Inc Industrials	Added	174,620	+142,295	$185,952,838	+712.0%	2	$844.07	0.61%
SMTC	Semtech Corp Technology	Reduced	1,133,268	-147,326	$183,419,425	+86.3%	6	$44.46	0.60%
AME	Ametek Inc Industrials	Reduced	723,798	-22,034	$175,115,688	+9.5%	26+	before history	0.57%
ABVX	Abivax S.A. Healthcare	Reduced	1,309,825	-13,113	$174,547,279	+18.5%	3	$111.29	0.57%
INSM	INSMED Inc Healthcare	Added	1,629,561	+161,102	$173,743,793	−27.6%	8	$129.30	0.57%
ITT	Itt Inc. Industrials	Added	830,382	+127,073	$164,216,344	+22.5%	25	$120.92	0.54%
GILD	Gilead Sciences, Inc. Healthcare	Added	1,287,629	+1,260,939	$162,679,047	+4273.3%	3	$131.55	0.53%
PTCT	Ptc Therapeutics, Inc. Healthcare	NEW	1,956,156	NEW	$159,563,644	NEW	1	$72.21	0.52%

Showing the top 50 of 278 positions. Create a free account to see every position, past quarters, search, filters and CSV export.

Covers the securities this platform tracks: U.S.-listed common stock and the put/call positions reported on it. A 13F can also report security types outside that coverage — preferred shares, bonds, warrants, untracked share classes — so the filing's own declared total can exceed the figures above. The source filing is linked at the top of this table.