Q2 2026 13F · SEC CIK 1177719

Westfield Capital Management Co LP

Asset managerFiled 2026-08-12 for Q2 2026. Open the filing ↗ · All SEC filings ↗

Reported 13F value: $30.6B
Reported positions: 278
Top holdings a year, 3 yrs: +30.8%
Average holding period: 4.9 yrs

Westfield Capital Management Co LP is an asset manager that reported 278 positions worth $30.6B in its Q2 2026 13F, filed 2026-08-12. Its largest holdings were Nvidia Corporation Com (NVDA, 5.3%), Alphabet Inc (GOOGL, 4.4%), Ascendis Pharma As Ord (ASND, 4.2%). A portfolio copying its top holdings returned 30.8% a year over the last 3 years, against 20.4% for the S&P 500.

Westfield Capital Management Co LP holdings largest 50 of 278 positions.

Weights are shares of the filer's total reported 13F value, compared with Q1 2026. Share changes may reflect splits; weight changes also reflect price moves. A 13F shows long US-listed positions only, up to 135 days after the fact.

Westfield Capital Management Co LP 13F holdings
Stock	% of 13F value	Q1 2026	Shares	Share change	Reported value
NVDANvidia Corporation Com	5.3%	4.6%	8,079,926	+27.9%	$1.6B
GOOGLAlphabet Inc	4.4%	2.4%	3,749,074	+85.0%	$1.3B
ASNDAscendis Pharma As Ord	4.2%	—	4,798,267	—	$1.3B
AXONAxon Enterprise Inc	2.7%	1.9%	1,491,490	+40.2%	$836.1M
FTAIFtai Aviation Ltd	2.6%	2.9%	2,937,228	+3.1%	$794.6M
AAPLApple Inc	2.4%	3.3%	2,573,774	-17.9%	$744.7M
FIXComfort Sys USA Inc	2.3%	3.6%	355,433	-42.8%	$704.5M
AVGOBroadcom Inc	1.9%	1.6%	1,556,522	+25.8%	$588.0M
MSFTMicrosoft Corp	1.7%	2.6%	1,414,294	-14.3%	$527.6M
HWMHowmet Aerospace Inc	1.7%	2.2%	1,921,476	-16.1%	$516.6M
LLYLilly Eli & Co	1.6%	1.4%	416,732	+14.3%	$499.8M
SNOWSnowflake Inc	1.4%	—	1,736,498	—	$441.9M
MKSIMks Inc.	1.3%	1.0%	928,617	-11.3%	$413.0M
METAMeta Platforms Inc Class A	1.2%	1.3%	677,389	+28.6%	$381.6M
VRTVertiv Holdings Co	1.2%	2.0%	1,054,361	-45.1%	$353.0M
GEVGe Vernova Inc	0.9%	0.7%	241,272	+21.1%	$283.5M
MUMicron Technology Inc	0.9%	—	228,203	—	$263.4M
VVisa Inc Com Cl A	0.9%	0.6%	762,403	+67.0%	$261.6M
APGApi Group Corp	0.9%	0.8%	6,154,301	+32.8%	$260.6M
TPRTapestry Inc	0.8%	1.3%	1,696,569	-22.8%	$248.3M
RYTMRhythm Pharmaceuticals Inc	0.8%	0.7%	2,208,595	+14.5%	$245.2M
LTHLife Time Group Holdings Inc	0.8%	—	5,995,254	—	$244.8M
TSMTaiwan Semiconductor Manufac	0.8%	0.7%	510,999	+3.5%	$244.0M
GHGuardant Health Inc	0.8%	—	1,624,459	—	$243.7M
PWRQuanta Svcs Inc Com	0.8%	0.8%	331,489	-0.1%	$238.7M
NOWServicenow Inc Com	0.8%	0.6%	2,373,711	+70.3%	$235.7M
AMDAdvanced Micro Devices Inc	0.8%	—	403,081	—	$234.2M
PANWPalo Alto Networks Inc	0.7%	—	658,331	—	$224.5M
WWDWoodward Inc	0.7%	—	526,505	—	$224.0M
ANETArista Networks Inc	0.7%	—	1,317,096	—	$223.7M
LPLALpl Financial Holdings Inc	0.7%	1.1%	793,061	-10.0%	$223.4M
RKLBRocket Lab Corp Com	0.7%	0.9%	2,114,005	-33.4%	$214.9M
ASAmer Sports Inc	0.7%	0.5%	6,344,923	+61.1%	$214.7M
NETCloudflare Inc	0.7%	—	835,502	—	$204.9M
AMZNAmazon Com Inc Com	0.7%	2.0%	859,806	-62.3%	$204.9M
GRMNGarmin Ltd	0.7%	—	861,057	—	$204.5M
RRXRegal Rexnord Corp.	0.7%	0.5%	856,976	+25.7%	$204.1M
NTRANatera Inc Com	0.6%	0.6%	726,628	-3.7%	$197.2M
MSMorgan Stanley Com New	0.6%	—	940,560	—	$196.6M
CRSCarpenter Technology Corp	0.6%	—	314,082	—	$193.7M
IOTSamsara, Inc.	0.6%	0.7%	5,836,459	+15.1%	$189.3M
DTDynatrace Inc	0.6%	0.7%	4,249,229	+0.9%	$186.6M
CATCaterpillar Inc Com	0.6%	—	174,620	—	$186.0M
SMTCSemtech Corp	0.6%	—	1,133,268	—	$183.4M
AMEAmetek Inc	0.6%	0.7%	723,798	-3.0%	$175.1M
ABVXAbivax SA	0.6%	0.6%	1,309,825	-1.0%	$174.5M
INSMInsmed Inc	0.6%	1.0%	1,629,561	+11.0%	$173.7M
ITTItt Inc	0.5%	0.6%	830,382	+18.1%	$164.2M
GILDGilead Sciences	0.5%	—	1,287,629	—	$162.7M
PTCTPtc Therapeutics Inc	0.5%	—	1,956,156	—	$159.6M

What Westfield Capital Management Co LP bought and sold in Q2 2026, against Q1 2026.

New positions

Q1 2026's filing was too long to tell new positions apart.

Share counts compared with the Q1 2026 13F; a split also changes share counts. The latest filing lists more than 50 positions, so a position that left the top 50 may still be held.

How the holdings did against the S&P 500.

1 year: +29.9% /yr; S&P 500 +20.1%
3 years: +30.8% /yr; S&P 500 +20.4%
5 years: +16.8% /yr; S&P 500 +11.6%

A portfolio of the filer's 20 largest 13F positions, weighted by value and rebuilt each quarter on the day the filing became public. 13Fs show long US-listed positions only, so this is an estimate of the stock picks, not the fund's reported returns.

Reported 13F value by quarter.

13F value by quarter
Quarter	13F value	Positions
Q2 2026	$30.6B	278
Q1 2026	$23.8B	250
Q4 2025	$24.0B	241
Q3 2025	$23.8B	235
Q2 2025	$23.8B	239
Q1 2025	$20.5B	244
Q4 2024	$23.0B	239
Q3 2024	$22.1B	247
Q2 2024	$20.4B	248
Q1 2024	$19.0B	244
Q4 2023	$17.2B	239
Q3 2023	$14.7B	234

Questions about Westfield Capital Management Co LP's portfolio

What stocks does Westfield Capital Management Co LP own?

Westfield Capital Management Co LP's latest 13F, for Q2 2026 and filed Aug 12, 2026, lists 278 positions worth $30.6B. The largest are Nvidia Corporation Com (NVDA) at 5.3%, Alphabet Inc (GOOGL) at 4.4%, Ascendis Pharma As Ord (ASND) at 4.2%, Axon Enterprise Inc (AXON) at 2.7% and Ftai Aviation Ltd (FTAI) at 2.6%.

What did Westfield Capital Management Co LP buy last quarter?

In Q2 2026, Westfield Capital Management Co LP added Alphabet Inc (GOOGL) (+85.0% shares), Servicenow Inc Com (NOW) (+70.3% shares) and Visa Inc Com Cl A (V) (+67.0% shares), compared with its Q1 2026 filing.

What did Westfield Capital Management Co LP sell last quarter?

In Q2 2026, Westfield Capital Management Co LP cut from its top 50 Ascendis Pharma A/s, cut from its top 50 Vaxcyte Inc (PCVX), cut from its top 50 Netflix Inc Total (NFLX), cut from its top 50 Ares Management Corporation (ARES), cut from its top 50 Marvell Technology Inc (MRVL), Amazon Com Inc Com (AMZN) (-62.3% shares), Vertiv Holdings Co (VRT) (-45.1% shares) and Comfort Sys USA Inc (FIX) (-42.8% shares), compared with its Q1 2026 filing.

How has Westfield Capital Management Co LP's portfolio performed?

A portfolio copying Westfield Capital Management Co LP's 20 largest 13F holdings each quarter, from the day each filing was public, returned +30.8% a year over the last 3 years, against +20.4% for the S&P 500. Over 1 year: +29.9% against +20.1%. Over 5 years: +16.8% a year against +11.6%.

When is Westfield Capital Management Co LP's next 13F filing due?

13F filings are due 45 days after each quarter ends. Westfield Capital Management Co LP's filing for the quarter ending Sep 30, 2026 is due by Nov 14, 2026; this page updates the day after it is published.