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 (NVDA, 5.3%), Alphabet Inc (GOOGL, 4.4%), Ascendis Pharma A/s (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	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 A/s	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
LLYEli Lilly & 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	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	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	0.8%	0.8%	331,489	-0.1%	$238.7M
NOWServicenow Inc	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 Finl Hldgs Inc	0.7%	1.1%	793,061	-10.0%	$223.4M
RKLBRocket Lab Corp	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	0.7%	2.0%	859,806	-62.3%	$204.9M
GRMNGarmin Ltd	0.7%	—	861,057	—	$204.5M
RRXRegal Rexnord Corporation	0.7%	0.5%	856,976	+25.7%	$204.1M
NTRANatera Inc	0.6%	0.6%	726,628	-3.7%	$197.2M
MSMorgan Stanley	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	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	0.5%	0.6%	830,382	+18.1%	$164.2M
GILDGilead Sciences Inc	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.

Added to

GOOGL Alphabet Inc+85.0% shares
NOW Servicenow Inc+70.3% shares
V Visa Inc+67.0% shares
AS Amer Sports Inc+61.1% shares
AXON Axon Enterprise Inc+40.2% shares
APG Api Group Corp+32.8% shares
META Meta Platforms Inc+28.6% shares
NVDA Nvidia Corporation+27.9% shares

Reduced

AMZN Amazon Com Inc-62.3% shares
VRT Vertiv Holdings Co-45.1% shares
FIX Comfort Sys USA Inc-42.8% shares
RKLB Rocket Lab Corp-33.4% shares
TPR Tapestry Inc-22.8% shares
AAPL Apple Inc-17.9% shares
HWM Howmet Aerospace Inc-16.1% shares
MSFT Microsoft Corp-14.3% shares

Left the top 50

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, bought the trading day after each 13F was filed and held until the next one was: what copying this filer could have earned. 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 (NVDA) at 5.3%, Alphabet Inc (GOOGL) at 4.4%, Ascendis Pharma A/s (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 (NOW) (+70.3% shares) and Visa Inc (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. (NFLX), cut from its top 50 Ares Management Corp (ARES), cut from its top 50 Marvell Technology Inc (MRVL), Amazon Com Inc (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.