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Asset manager

Westfield Capital Management Co LP

13F for the quarter to June 30, 2026, filed August 12, 2026 · SEC CIK 1177719

Reported value
$30.6bn
99% in companies we cover
Positions we cover
263
Largest NVDA 5.3%
Copy, a year
+14.2%
S&P 500 +14.1%
Copy Sharpe ratio
0.68
S&P 500 0.78

How copying its 13F would have done

$10.0k$20.0k$40.0k 2013201520172019202120232025 $57.4k$57.0k
CopyS&P 500 $10,000 copying Westfield Capital Management Co LP's filed holdings in companies we cover from August 16, 2013, buying on the first trading day after each 13F was filed and holding until the next, against the S&P 500 (total return). Marked weekly, log scale. Before costs and taxes; misses trading within each quarter and anything 13F does not show (shorts, cash, bonds, non-US holdings).

Biggest drop −34.6% (S&P 500 −31.8%); beta 1.15; alpha −1.2% a year (t = −0.78); last 12 months +6.5% against +12.1%.

Reported value by quarter

Westfield Capital Management Co LP: 13F reported value Total value of all positions in each quarter's 13F, as filed (values before 2023 were filed in thousands of dollars and are converted).
$0 $5T $10T $15T Reported value, 2013-06-30: $14.5B Reported value, 2013-09-30: $15.6B Reported value, 2013-12-31: $17B Reported value, 2014-03-31: $16.7B Reported value, 2014-06-30: $16.8B Reported value, 2014-09-30: $16.4B Reported value, 2014-12-31: $17B Reported value, 2015-03-31: $17.4B Reported value, 2015-06-30: $16.4B Reported value, 2015-09-30: $14.1B Reported value, 2015-12-31: $14.9B Reported value, 2016-03-31: $13.1B Reported value, 2016-06-30: $12.1B Reported value, 2016-09-30: $12.4B Reported value, 2016-12-31: $11.4B Reported value, 2017-03-31: $11.6B Reported value, 2017-06-30: $11.7B Reported value, 2017-09-30: $13B Reported value, 2017-12-31: $13.1B Reported value, 2018-03-31: $13B Reported value, 2018-06-30: $13.4B Reported value, 2018-09-30: $14.2B Reported value, 2018-12-31: $11.7B Reported value, 2019-03-31: $13.1B Reported value, 2019-06-30: $13.3B Reported value, 2019-09-30: $12.5B Reported value, 2019-12-31: $14B Reported value, 2020-03-31: $11.4B Reported value, 2020-06-30: $14.5B Reported value, 2020-09-30: $15.4B Reported value, 2020-12-31: $16.9B Reported value, 2021-03-31: $16.1B Reported value, 2021-06-30: $16.7B Reported value, 2021-09-30: $16.6B Reported value, 2021-12-31: $16.8B Reported value, 2022-03-31: $15.6B Reported value, 2022-06-30: $12.7B Reported value, 2022-09-30: $12.6B Reported value, 2022-12-31: $13T Reported value, 2023-03-31: $14.2B Reported value, 2023-06-30: $15.7B Reported value, 2023-09-30: $14.7B Reported value, 2023-12-31: $17.2B Reported value, 2024-03-31: $19B Reported value, 2024-06-30: $20.4B Reported value, 2024-09-30: $22.1B Reported value, 2024-12-31: $23B Reported value, 2025-03-31: $20.5B Reported value, 2025-06-30: $23.8B Reported value, 2025-09-30: $23.8B Reported value, 2025-12-31: $24B Reported value, 2026-03-31: $23.8B Reported value, 2026-06-30: $30.6B 2013-06-30 2016-03-31 2018-12-31 2021-09-30 2026-06-30 $30.6B
View chart data
Period Reported value
2013-06-30 $14.5B
2013-09-30 $15.6B
2013-12-31 $17B
2014-03-31 $16.7B
2014-06-30 $16.8B
2014-09-30 $16.4B
2014-12-31 $17B
2015-03-31 $17.4B
2015-06-30 $16.4B
2015-09-30 $14.1B
2015-12-31 $14.9B
2016-03-31 $13.1B
2016-06-30 $12.1B
2016-09-30 $12.4B
2016-12-31 $11.4B
2017-03-31 $11.6B
2017-06-30 $11.7B
2017-09-30 $13B
2017-12-31 $13.1B
2018-03-31 $13B
2018-06-30 $13.4B
2018-09-30 $14.2B
2018-12-31 $11.7B
2019-03-31 $13.1B
2019-06-30 $13.3B
2019-09-30 $12.5B
2019-12-31 $14B
2020-03-31 $11.4B
2020-06-30 $14.5B
2020-09-30 $15.4B
2020-12-31 $16.9B
2021-03-31 $16.1B
2021-06-30 $16.7B
2021-09-30 $16.6B
2021-12-31 $16.8B
2022-03-31 $15.6B
2022-06-30 $12.7B
2022-09-30 $12.6B
2022-12-31 $13T
2023-03-31 $14.2B
2023-06-30 $15.7B
2023-09-30 $14.7B
2023-12-31 $17.2B
2024-03-31 $19B
2024-06-30 $20.4B
2024-09-30 $22.1B
2024-12-31 $23B
2025-03-31 $20.5B
2025-06-30 $23.8B
2025-09-30 $23.8B
2025-12-31 $24B
2026-03-31 $23.8B
2026-06-30 $30.6B

Holdings and moves

CompanyShare of portfolioValueSharesChange in shares
NVDANVIDIA Corporation5.28%$1.6bn8.08M+27.9% Added
GOOGLAlphabet Inc. (Class A)4.38%$1.3bn3.75M+85.0% Added
ASNDAscendis Pharma A/s4.18%$1.3bn4.80MNew
AXONAxon Enterprise2.73%$836.1m1.49M+40.2% Added
FTAIFTAI Aviation Ltd.2.60%$794.6m2.94M+3.1% Added
AAPLApple Inc.2.43%$744.7m2.57M−17.9% Reduced
FIXComfort Systems USA2.30%$704.5m355.4K−42.8% Reduced
AVGOBroadcom1.92%$588.0m1.56M+25.8% Added
MSFTMicrosoft Corporation1.72%$527.6m1.41M−14.3% Reduced
HWMHowmet Aerospace1.69%$516.6m1.92M−16.1% Reduced
LLYLilly (Eli)1.63%$499.8m416.7K+14.3% Added
SNOWSnowflake Inc.1.44%$441.9m1.74M+141.6% Added
MKSIMKS Inc1.35%$413.0m928.6K−11.3% Reduced
METAMeta Platforms1.25%$381.6m677.4K+28.6% Added
VRTVertiv1.15%$353.0m1.05M−45.1% Reduced
GEVGE Vernova0.93%$283.5m241.3K+21.1% Added
MUMicron Technology0.86%$263.4m228.2K+127.2% Added
VVisa Inc.0.85%$261.6m762.4K+67.0% Added
APGApi Group Corp0.85%$260.6m6.15M+32.8% Added
TPRTapestry, Inc.0.81%$248.3m1.70M−22.8% Reduced
RYTMRhythm Pharmaceuticals, Inc.0.80%$245.2m2.21M+14.5% Added
LTHLife Time Group Holdings, Inc.0.80%$244.8m6.00M+88.2% Added
TSMTaiwan Semiconductor Manufacturing Co LTD0.80%$244.0m511.0K+3.5% Added
GHGuardant Health, Inc.0.80%$243.7m1.62M+19.2% Added
PWRQuanta Services0.78%$238.7m331.5K−0.1%
NOWServiceNow0.77%$235.7m2.37M+70.3% Added
AMDAdvanced Micro Devices0.77%$234.2m403.1K+7929.5% Added
PANWPalo Alto Networks0.73%$224.5m658.3K+3.4% Added
WWDWoodward, Inc.0.73%$224.0m526.5K+93.4% Added
ANETArista Networks0.73%$223.7m1.32M+68.8% Added
LPLALPL Financial Holdings Inc.0.73%$223.4m793.1K−10.0% Reduced
RKLBRocket Lab Corp0.70%$214.9m2.11M−33.4% Reduced
ASAmer Sports, Inc.0.70%$214.7m6.34M+61.1% Added
NETCloudflare, Inc.0.67%$204.9m835.5K+54.3% Added
AMZNAmazon0.67%$204.9m859.8K−62.3% Reduced
GRMNGarmin0.67%$204.5m861.1K+128.8% Added
RRXRegal Rexnord Corp0.67%$204.1m857.0K+25.7% Added
NTRANatera, Inc.0.64%$197.2m726.6K−3.7% Reduced
MSMorgan Stanley0.64%$196.6m940.6K+89.4% Added
CRSCarpenter Technology Corp0.63%$193.7m314.1KNew
IOTSamsara Inc.0.62%$189.3m5.84M+15.1% Added
DTDynatrace, Inc.0.61%$186.6m4.25M+0.9% Added
CATCaterpillar Inc.0.61%$186.0m174.6K+440.2% Added
SMTCSemtech Corp0.60%$183.4m1.13M−11.5% Reduced
AMEAmetek0.57%$175.1m723.8K−3.0% Reduced
ABVXAbivax S.a.0.57%$174.5m1.31M−1.0% Reduced
INSMInsmed Inc0.57%$173.7m1.63M+11.0% Added
ITTITT Inc.0.54%$164.2m830.4K+18.1% Added
GILDGilead Sciences0.53%$162.7m1.29M+4724.4% Added
PTCTPTC Therapeutics, Inc.0.52%$159.6m1.96MNew
BROSDutch Bros Inc.0.51%$156.8m2.18M−5.6% Reduced
CELHCelsius Holdings, Inc.0.51%$155.9m5.32M+41.3% Added
MTZMastec Inc0.51%$155.8m374.5K+49.8% Added
SNSharkninja, Inc.0.50%$153.5m1.01M+11.5% Added
CSXCSX Corporation0.49%$149.9m3.15M+90.2% Added
FCFSFirstcash Holdings, Inc.0.49%$149.9m693.1K+60.4% Added
KEYKeyCorp0.49%$149.7m6.49M+25.0% Added
MCHPMicrochip Technology Inc0.49%$149.5m1.64M+68.9% Added
AMATApplied Materials0.49%$148.6m205.6K+21865.0% Added
MARMarriott International0.48%$147.9m399.0K+160.4% Added
PCVXVaxcyte, Inc.0.47%$143.7m2.47M−32.2% Reduced
GLGlobe Life0.45%$137.8m771.0K−8.5% Reduced
FTITechnipFMC plc0.45%$136.6m2.06M+1.3% Added
XPOXPO, Inc.0.42%$129.1m629.0K+10.0% Added
LEGNLegend Biotech Corp0.42%$127.9m4.43M−23.1% Reduced
PEverpure0.41%$127.0m1.61M−14.0% Reduced
LRCXLam Research0.40%$123.8m285.6KNew
JLLJones Lang Lasalle Inc0.40%$123.5m398.5K+14.6% Added
ALABAstera Labs, Inc.0.39%$120.4m249.3K−71.0% Reduced
ROKRockwell Automation0.38%$117.4m237.1K+15.0% Added
IEXIDEX Corporation0.38%$116.6m513.6K+20.5% Added
COHRCoherent Corp.0.38%$114.8m291.0K−26.6% Reduced
LGNLegence Corp.0.37%$114.4m1.34M−27.9% Reduced
LECOLincoln Electric Holdings Inc0.37%$114.4m430.7K+20.2% Added
ASMLAsml Holding NV0.37%$114.3m57.4KNew
PLPlanet Labs PBC0.37%$113.6m3.43M+109.4% Added
ONTOOnto Innovation Inc.0.37%$113.3m299.4K−8.4% Reduced
CORCencora0.37%$113.2m400.1K−8.4% Reduced
RVMDRevolution Medicines, Inc.0.37%$112.5m600.8K−61.4% Reduced
SNDKSandisk0.36%$111.5m49.0KNew
AFRMAffirm Holdings, Inc.0.36%$110.3m1.35M+25.1% Added
LYVLive Nation Entertainment0.35%$108.2m590.8K−27.1% Reduced
NPOEnpro Inc.0.35%$108.0m286.6KNew
PRPermian Resources Corp0.35%$106.0m5.76M−23.1% Reduced
ARESAres Management0.35%$106.0m952.0K−39.5% Reduced
IMAXImax Corp0.35%$105.8m2.65M+13.5% Added
GWREGuidewire Software, Inc.0.34%$103.3m839.3K+72.5% Added
NXTNextpower Inc.0.33%$102.2m857.4K−22.6% Reduced
FROGJfrog Ltd0.33%$101.3m1.11MNew
SNPSSynopsys Inc0.33%$101.2m226.9K+70.8% Added
ROKURoku, Inc0.32%$99.0m716.6K−39.2% Reduced
PLXSPlexus Corp0.32%$96.8m321.8K−16.3% Reduced
AITApplied Industrial Technologies Inc0.32%$96.6m285.7K−1.2% Reduced
MSCIMSCI0.32%$96.3m172.0K−26.4% Reduced
HOODRobinhood Markets0.31%$95.8m955.5K+50.9% Added
ROSTRoss Stores0.31%$94.2m442.4K−6.3% Reduced
ADPTAdaptive Biotechnologies Corp0.30%$91.5m4.27M−21.5% Reduced
XENEXenon Pharmaceuticals Inc.0.30%$91.0m1.51M+7.5% Added
ORLYO'Reilly Automotive0.28%$85.9m933.3K+5.1% Added
CCitigroup0.28%$85.1m608.1K+1267.9% Added
PKGPackaging Corporation of America0.28%$84.9m356.3K+17.3% Added
BIRKBirkenstock Holding plc0.28%$84.6m1.97M−15.9% Reduced
PLMRPalomar Holdings, Inc.0.28%$84.5m668.9K−21.7% Reduced
EWBCEast West Bancorp Inc0.27%$83.9m649.6K−19.4% Reduced
RRRRed Rock Resorts, Inc.0.27%$82.1m1.26M+2.7% Added
WTFCWintrust Financial Corp0.27%$81.0m504.0K+10.7% Added
CLHClean Harbors Inc0.26%$80.2m268.3K+2.8% Added
CWSTCasella Waste Systems Inc0.26%$78.8m812.5K−1.2% Reduced
TTMITTM Technologies Inc0.25%$77.8m416.1KNew
TRGPTarga Resources0.25%$77.0m287.1K−5.9% Reduced
FPSForgent Power Solutions, Inc.0.25%$76.6m1.37MNew
ALNYAlnylam Pharmaceuticals, Inc.0.25%$76.0m252.4K+2.8% Added
COCOVita Coco Company, Inc.0.25%$75.3m1.14M−1.2% Reduced
RBRKRubrik, Inc.0.25%$75.2m937.3KNew
AZOAutoZone0.24%$74.8m23.4K−17.5% Reduced
DASHDoorDash0.24%$74.1m401.7K−9.5% Reduced
WYNNWynn Resorts0.24%$73.9m761.4K+2.9% Added
IDXXIdexx Laboratories0.24%$73.7m139.9K+5.3% Added
SFMSprouts Farmers Market, Inc.0.24%$73.3m866.6KNew
PRAXPraxis Precision Medicines, Inc.0.24%$73.3m218.9K+32966.2% Added
CRMSalesforce0.24%$73.2m467.0K+71.7% Added
PRIMPrimoris Services Corp0.24%$73.1m737.5K−0.8% Reduced
DYDycom Industries Inc0.23%$71.8m142.0KNew
STEPStepstone Group Inc.0.23%$71.5m1.73M+46.8% Added
JBHTJ.B. Hunt0.23%$71.1m245.8K+7.5% Added
VSTVistra Corp.0.23%$70.7m445.7K−9.9% Reduced
GKOSGlaukos Corp0.22%$67.6m483.4K+0.2%
MTSIMacom Technology Solutions Holdings, Inc.0.22%$66.9m176.0K+32.8% Added
TERTeradyne0.22%$66.0m136.5KNew
SAIASaia Inc0.21%$64.7m153.6K−1.3% Reduced
NXPINXP Semiconductors0.21%$63.9m227.4K−8.3% Reduced
STSensata Technologies Holding plc0.21%$63.7m1.33MNew
HQYHealthequity, Inc.0.21%$63.5m703.3K−1.3% Reduced
BTSGBrightspring Health Services, Inc.0.20%$62.6m897.8KNew
RLAYRelay Therapeutics, Inc.0.20%$62.6m3.34MNew
HLIHoulihan Lokey, Inc.0.20%$62.2m463.4K−14.8% Reduced
ENTGEntegris Inc0.20%$62.0m345.0K−7.2% Reduced
CORZCore Scientific, Inc.0.20%$61.7m2.41M+62.8% Added
RDNTRadnet, Inc.0.20%$60.2m975.5K+83.4% Added
ORKAOruka Therapeutics, Inc.0.20%$60.1m631.4K+101.7% Added
CRDOCredo Technology Group Holding Ltd0.19%$59.0m217.0K−76.6% Reduced
BLDRBuilders Firstsource, Inc.0.19%$58.7m656.4KNew
LSCCLattice Semiconductor Corp0.19%$58.4m381.8K−32.2% Reduced
DSGXDescartes Systems Group Inc0.19%$57.8m835.4K+4.2% Added
AVNTAvient Corp0.19%$57.3m1.55M−1.2% Reduced
BRZEBraze, Inc.0.18%$56.8m2.62M−34.1% Reduced
FNFabrinet0.18%$54.7m97.4K−65.8% Reduced
LNGCheniere Energy, Inc.0.18%$54.6m228.5K−50.2% Reduced
PODDInsulet Corporation0.17%$53.7m352.7K+20870.1% Added
RBLXRoblox Corp0.17%$53.6m985.8KNew
CompanyBought (value)Shares
ASNDAscendis Pharma A/s$1.3bn4.80M
GOOGLAlphabet Inc. (Class A)$615.5m1.72M
NVDANVIDIA Corporation$352.7m1.76M
SNOWSnowflake Inc.$259.0m1.02M
AXONAxon Enterprise$239.6m427.4K
AMDAdvanced Micro Devices$231.2m398.1K
CRSCarpenter Technology Corp$193.7m314.1K
PTCTPTC Therapeutics, Inc.$159.6m1.96M
GILDGilead Sciences$159.3m1.26M
CATCaterpillar Inc.$151.5m142.3K
AMATApplied Materials$148.0m204.7K
MUMicron Technology$147.5m127.8K
LRCXLam Research$123.8m285.6K
AVGOBroadcom$120.7m319.6K
GRMNGarmin$115.1m484.7K

Change in shares on the previous quarter's 13F, valued at this quarter's reported price.

CompanySold (value)Shares
FIXComfort Systems USA−$526.2m−265.5K
MRVLMarvell Technology−$494.5m−1.66M
BEBloom Energy−$357.5m−1.18M
AMZNAmazon−$338.4m−1.42M
ALABAstera Labs, Inc.−$295.0m−610.8K
VRTVertiv−$290.4m−867.3K
CRDOCredo Technology Group Holding Ltd−$192.9m−709.2K
RVMDRevolution Medicines, Inc.−$179.0m−955.8K
AAPLApple Inc.−$161.9m−559.3K
RCLRoyal Caribbean Group−$119.9m−377.6K
NFLXNetflix−$119.9m−1.68M
TSLATesla, Inc.−$111.7m−265.7K
KTOSKratos Defense & Security Solutions, Inc.−$110.2m−1.56M
AIGAmerican International Group−$109.8m−1.46M
RKLBRocket Lab Corp−$107.6m−1.06M

Change in shares on the previous quarter's 13F, valued at this quarter's reported price.

CompanyValue last quarterShares
KTOSKratos Defense & Security Solutions, Inc.$110.2m1.56M
AIGAmerican International Group$109.8m1.46M
PLTRPalantir Technologies Inc.$98.7m674.6K
WGSGenedx Holdings Corp.$87.9m1.37M
FFIVF5, Inc.$86.4m298.5K
CHRWC.H. Robinson$71.3m429.5K
LOWLowe's$71.1m301.0K
ZSZscaler, Inc.$60.0m427.9K
HUBSHubspot Inc$56.9m233.0K
IBPInstalled Building Products, Inc.$55.2m208.2K
MCOMoody's Corporation$53.9m123.6K
KKRKKR & Co.$51.6m558.1K
TECHBio-Techne$44.7m856.0K
FICOFair Isaac$42.6m39.9K
IONQIonQ, Inc.$39.6m1.37M
HLNEHamilton Lane Inc$36.2m364.2K
OPCHOption Care Health, Inc.$31.8m1.18M
TDGTransDigm Group$15.0m12.9K
WFCWells Fargo$7.0m87.7K
MTBM&T Bank$6.2m29.8K
RJFRaymond James Financial$5.8m40.1K
MCDMcDonald's$5.6m18.0K
MDTMedtronic$5.2m60.3K
EXPEExpedia Group$3.9m16.7K
PEPPepsiCo$3.5m22.8K
CAHCardinal Health$2.8m13.0K
ITGartner$2.3m14.4K
MNDYMonday.com Ltd.$924,00113.4K
GENIGenius Sports Ltd$917,675207.2K
IBMIBM$804,7353.3K
  • Technology32.6%
  • Industrials23.6%
  • Health Care16.3%
  • Consumer Discretionary7.9%
  • Financials7.3%
  • Communication Services7.1%
  • Materials1.6%
  • Energy1.5%
  • Consumer Staples1.1%
  • Real Estate0.5%
  • Utilities0.4%

Share of the value held in companies we cover, by sector.

PeriodCopy, a yearS&P 500SharpeS&P 500Biggest dropBeta
Whole backtestAugust 16, 2013 to November 2, 2026+14.2%+14.1%0.680.78−34.6%1.15
2018 onwardsJanuary 5, 2018 to November 2, 2026+13.2%+13.9%0.550.66−34.6%1.15
Last three yearsNovember 3, 2023 to November 2, 2026+18.3%+21.8%0.751.16−25.5%1.27
Last yearNovember 7, 2025 to November 2, 2026+9.7%+14.2%0.390.84−11.3%1.30

From SEC Form 13F data sets. A 13F lists long positions in US-listed shares at the quarter's end, filed up to 45 days later; it does not show shorts, cash, bonds, non-US holdings or trades within the quarter. Positions in companies outside our coverage are not listed here. Research, not investment advice.