Westfield Capital Management Co. LP
In its 13F for Q2 2026 (holdings as of June 30, 2026, filed August 12, 2026), Westfield Capital Management Co. LP reported 278 stock positions worth $30.6 billion. Its top holding was Nvidia (NVDA) at 5.3% of the portfolio, followed by Alphabet Class A (GOOGL, 4.4%) and Ascendis Pharma A/S (ASND, 4.2%). Compared with Q1 2026, it opened 68 new positions, sold out of 40, added to 98 and reduced 104. The biggest buy was Alphabet Class A (GOOGL, shares +85%) and the biggest sale Amazon.com (AMZN, shares −62%).
- Most Recent 13F
- Q2 2026
- Location
- BOSTON, MA
- CIK
- 0001177719
- Portfolio Value
- $30.6B (Q2 2026)
- SEC Filing
- 0001177719-26-000021 ↗ filed Aug 12, 2026
Holdings Value
Holdings 278 stocks · $30.6B
| NVDA Nvidia Corp. | 5.28% | 8,079,926 | $1.6B | Add +27.9% |
| GOOGL Alphabet Inc. Class A | 4.38% | 3,749,074 | $1.3B | Add +85.0% |
| ASND Ascendis Pharma A/S | 4.18% | 4,798,267 | $1.3B | Reduce -0.3% |
| AXON Axon Enterprise Inc. | 2.73% | 1,491,490 | $836.1M | Add +40.2% |
| FTAI Ftai Aviation Ltd. | 2.60% | 2,937,228 | $794.6M | Add +3.1% |
| AAPL Apple Inc. | 2.43% | 2,573,774 | $744.7M | Reduce -17.9% |
| FIX Comfort Systems USA Inc. | 2.30% | 355,433 | $704.5M | Reduce -42.8% |
| AVGO Broadcom Inc. | 1.92% | 1,556,522 | $588.0M | Add +25.8% |
| MSFT Microsoft Corp. | 1.72% | 1,414,294 | $527.6M | Reduce -14.3% |
| HWM Howmet Aerospace Inc. | 1.69% | 1,921,476 | $516.6M | Reduce -16.1% |
| LLY Eli Lilly & Co. | 1.63% | 416,732 | $499.8M | Add +14.3% |
| SNOW Snowflake Inc. | 1.44% | 1,736,498 | $441.9M | Add +141.6% |
| MKSI MKS Inc. | 1.35% | 928,617 | $413.0M | Reduce -11.3% |
| META Meta Platforms Inc. Class A | 1.25% | 677,389 | $381.6M | Add +28.6% |
| VRT Vertiv Holdings Co. Class A | 1.15% | 1,054,361 | $353.0M | Reduce -45.1% |
| GEV GE Vernova Inc. | 0.93% | 241,272 | $283.5M | Add +21.1% |
| MU Micron Technology Inc. | 0.86% | 228,203 | $263.4M | Add +127.2% |
| V Visa Inc. Class A | 0.85% | 762,403 | $261.6M | Add +67.0% |
| APG Api Group Corp. | 0.85% | 6,154,301 | $260.6M | Add +32.8% |
| TPR Tapestry Inc. | 0.81% | 1,696,569 | $248.3M | Reduce -22.8% |
| RYTM Rhythm Pharmaceuticals Inc. | 0.80% | 2,208,595 | $245.2M | Add +14.5% |
| LTH Life Time Group Holdings Inc. | 0.80% | 5,995,254 | $244.8M | Add +88.2% |
| TSM Taiwan Semiconductor-SP ADR | 0.80% | 510,999 | $244.0M | Add +3.5% |
| GH Guardant Health Inc. | 0.80% | 1,624,459 | $243.7M | Add +19.2% |
| PWR Quanta Services Inc. | 0.78% | 331,489 | $238.7M | Reduce -0.1% |
| NOW ServiceNow Inc. | 0.77% | 2,373,711 | $235.7M | Add +70.3% |
| AMD Advanced Micro Devices | 0.76% | 403,081 | $234.2M | Add +7929.5% |
| PANW Palo Alto Networks Inc. | 0.73% | 658,331 | $224.5M | Add +3.4% |
| WWD Woodward Inc. | 0.73% | 526,505 | $224.0M | Add +93.4% |
| ANET Arista Networks Inc. | 0.73% | 1,317,096 | $223.7M | Add +68.8% |
| LPLA LPL Financial Holdings Inc. | 0.73% | 793,061 | $223.4M | Reduce -10.0% |
| RKLB Rocket Lab Corp. | 0.70% | 2,114,005 | $214.9M | Reduce -33.4% |
| AS Amer Sports Inc. | 0.70% | 6,344,923 | $214.7M | Add +61.1% |
| NET Cloudflare Inc. Class A | 0.67% | 835,502 | $204.9M | Add +54.3% |
| AMZN Amazon.com Inc. | 0.67% | 859,806 | $204.9M | Reduce -62.3% |
| GRMN Garmin Ltd. | 0.67% | 861,057 | $204.5M | Add +128.8% |
| RRX Regal Rexnord Corp. | 0.67% | 856,976 | $204.1M | Add +25.7% |
| NTRA Natera Inc. | 0.64% | 726,628 | $197.2M | Reduce -3.7% |
| MS Morgan Stanley | 0.64% | 940,560 | $196.6M | Add +89.4% |
| CRS Carpenter Technology | 0.63% | 314,082 | $193.7M | New |
| IOT Samsara Inc. Class A | 0.62% | 5,836,459 | $189.3M | Add +15.1% |
| DT Dynatrace Inc. | 0.61% | 4,249,229 | $186.6M | Add +0.9% |
| CAT Caterpillar Inc. | 0.61% | 174,620 | $186.0M | Add +440.2% |
| SMTC Semtech Corp. | 0.60% | 1,133,268 | $183.4M | Reduce -11.5% |
| AME Ametek Inc. | 0.57% | 723,798 | $175.1M | Reduce -3.0% |
| ABVX Abivax SA-ADR | 0.57% | 1,309,825 | $174.5M | Reduce -1.0% |
| INSM Insmed Inc. | 0.57% | 1,629,561 | $173.7M | Add +11.0% |
| ITT Itt Inc. | 0.54% | 830,382 | $164.2M | Add +18.1% |
| GILD Gilead Sciences Inc. | 0.53% | 1,287,629 | $162.7M | Add +4724.4% |
| PTCT PTC Therapeutics Inc. | 0.52% | 1,956,156 | $159.6M | New |
| BROS Dutch Bros Inc. Class A | 0.51% | 2,184,001 | $156.8M | Reduce -5.6% |
| CELH Celsius Holdings Inc. | 0.51% | 5,324,481 | $155.9M | Add +41.3% |
| MTZ Mastec Inc. | 0.51% | 374,457 | $155.8M | Add +49.8% |
| SN Sharkninja Inc. | 0.50% | 1,008,349 | $153.5M | Add +11.5% |
| CSX CSX Corp. | 0.49% | 3,154,419 | $149.9M | Add +90.2% |
| FCFS Firstcash Holdings Inc. | 0.49% | 693,085 | $149.9M | Add +60.4% |
| KEY Keycorp | 0.49% | 6,493,467 | $149.7M | Add +25.0% |
| MCHP Microchip Technology Inc. | 0.49% | 1,639,111 | $149.5M | Add +68.9% |
| AMAT Applied Materials Inc. | 0.49% | 205,592 | $148.6M | Add +21865.0% |
| MAR Marriott International Class A | 0.48% | 398,962 | $147.9M | Add +160.4% |
| PCVX Vaxcyte Inc. | 0.47% | 2,472,428 | $143.7M | Reduce -32.2% |
| GL Globe Life Inc. | 0.45% | 770,990 | $137.8M | Reduce -8.5% |
| FTI Technipfmc PLC | 0.45% | 2,059,689 | $136.6M | Add +1.3% |
| XPO Xpo Inc. | 0.42% | 629,011 | $129.1M | Add +10.0% |
| LEGN Legend Biotech Corp.-ADR | 0.42% | 4,430,063 | $127.9M | Reduce -23.1% |
| P Everpure Inc. Class A | 0.41% | 1,611,958 | $127.0M | Reduce -14.0% |
| LRCX Lam Research Corp. | 0.40% | 285,614 | $123.8M | New |
| JLL Jones Lang Lasalle Inc. | 0.40% | 398,453 | $123.5M | Add +14.6% |
| ALAB Astera Labs Inc. | 0.39% | 249,299 | $120.4M | Reduce -71.0% |
| ROK Rockwell Automation Inc. | 0.38% | 237,136 | $117.4M | Add +15.0% |
| IEX Idex Corp. | 0.38% | 513,564 | $116.6M | Add +20.6% |
| COHR Coherent Corp. | 0.38% | 291,040 | $114.8M | Reduce -26.6% |
| LGN Legence Corp. Class A | 0.37% | 1,341,963 | $114.4M | Reduce -27.9% |
| LECO Lincoln Electric Holdings | 0.37% | 430,681 | $114.4M | Add +20.3% |
| ASML ASML Holding NV-NY Reg SHS filed as ASML HLDG NV | 0.37% | 57,430 | $114.3M | New |
| PL Planet Labs PBC | 0.37% | 3,428,007 | $113.6M | Add +109.4% |
| ONTO Onto Innovation Inc. | 0.37% | 299,383 | $113.3M | Reduce -8.4% |
| COR Cencora Inc. | 0.37% | 400,058 | $113.2M | Reduce -8.4% |
| RVMD Revolution Medicines Inc. | 0.37% | 600,821 | $112.5M | Reduce -61.4% |
| SNDK Sandisk Corp. | 0.36% | 49,024 | $111.5M | New |
| AFRM Affirm Holdings Inc. | 0.36% | 1,352,200 | $110.3M | Add +25.1% |
| LYV Live Nation Entertainment Inc. | 0.35% | 590,764 | $108.2M | Reduce -27.1% |
| NPO Enpro Inc. | 0.35% | 286,554 | $108.0M | New |
| PR Permian Resources Corp. Class A | 0.35% | 5,756,888 | $106.0M | Reduce -23.1% |
| ARES Ares Management Corp. Class A | 0.35% | 952,032 | $106.0M | Reduce -39.5% |
| IMAX Imax Corp. | 0.35% | 2,654,014 | $105.8M | Add +13.5% |
| GWRE Guidewire Software Inc. | 0.34% | 839,337 | $103.3M | Add +72.5% |
| NXT Nextpower Inc. | 0.33% | 857,399 | $102.2M | Reduce -22.6% |
| FROG Jfrog Ltd. | 0.33% | 1,114,561 | $101.3M | New |
| SNPS Synopsys Inc. | 0.33% | 226,856 | $101.2M | Add +70.8% |
| ROKU Roku Inc. | 0.32% | 716,557 | $99.0M | Reduce -39.2% |
| PLXS Plexus Corp. | 0.32% | 321,808 | $96.8M | Reduce -16.3% |
| AIT Applied Industrial Tech Inc. | 0.32% | 285,691 | $96.6M | Reduce -1.2% |
| MSCI MSCI Inc. | 0.31% | 171,958 | $96.3M | Reduce -26.4% |
| HOOD Robinhood Markets Inc. Class A | 0.31% | 955,544 | $95.8M | Add +50.9% |
| ROST Ross Stores Inc. | 0.31% | 442,420 | $94.2M | Reduce -6.3% |
| ADPT Adaptive Biotechnologies | 0.30% | 4,267,645 | $91.5M | Reduce -21.5% |
| XENE Xenon Pharmaceuticals Inc. | 0.30% | 1,507,294 | $91.0M | Add +7.5% |
| ORLY O'reilly Automotive Inc. | 0.28% | 933,255 | $85.9M | Add +5.1% |
| C Citigroup Inc. | 0.28% | 608,124 | $85.1M | Add +1267.9% |
Portfolio Sells Q1 2026 → Q2 2026
| AMZN Amazon.com Inc. | Reduce -62.3% | 0.67% | −1.32 |
| FIX Comfort Systems USA Inc. | Reduce -42.8% | 2.30% | −1.29 |
| AAPL Apple Inc. | Reduce -17.9% | 2.43% | −0.90 |
| VRT Vertiv Holdings Co. Class A | Reduce -45.1% | 1.15% | −0.87 |
| MSFT Microsoft Corp. | Reduce -14.3% | 1.72% | −0.84 |
| NFLX Netflix Inc. | Reduce -85.2% | 0.07% | −0.73 |
| MRVL Marvell Technology Inc. | Reduce -99.2% | 0.01% | −0.68 |
| BE Bloom Energy Corp. Class A | Reduce -99.1% | 0.01% | −0.67 |
| HWM Howmet Aerospace Inc. | Reduce -16.1% | 1.69% | −0.53 |
| TPR Tapestry Inc. | Reduce -22.8% | 0.81% | −0.49 |
| KTOS Kratos Defense & Security | Sold out | 0.00% | −0.46 |
| AIG American International Group | Sold out | 0.00% | −0.46 |
| RCL Royal Caribbean Cruises Ltd. | Reduce -74.7% | 0.13% | −0.45 |
| FN Fabrinet | Reduce -65.8% | 0.18% | −0.44 |
| ASND Ascendis Pharma A/S | Reduce -0.3% | 4.18% | −0.44 |
| TSLA Tesla Inc. | Reduce -84.0% | 0.07% | −0.42 |
| HLT Hilton Worldwide Holdings Inc. | Reduce -67.2% | 0.16% | −0.42 |
| PCVX Vaxcyte Inc. | Reduce -32.2% | 0.47% | −0.42 |
| PLTR Palantir Technologies Inc. Class A | Sold out | 0.00% | −0.41 |
| LPLA LPL Financial Holdings Inc. | Reduce -10.0% | 0.73% | −0.38 |
| ARES Ares Management Corp. Class A | Reduce -39.5% | 0.35% | −0.37 |
| WGS Genedx Holdings Corp. | Sold out | 0.00% | −0.37 |
| LNG Cheniere Energy Inc. | Reduce -50.2% | 0.18% | −0.37 |
| FFIV F5 Inc. | Sold out | 0.00% | −0.36 |
| FITB Fifth Third Bancorp | Reduce -70.2% | 0.13% | −0.33 |
| PR Permian Resources Corp. Class A | Reduce -23.1% | 0.35% | −0.32 |
| KRMN Karman Holdings Inc. | Reduce -96.4% | 0.01% | −0.32 |
| CHRW C.H. Robinson Worldwide Inc. | Sold out | 0.00% | −0.30 |
| LOW Lowe's Cos Inc. | Sold out | 0.00% | −0.30 |
| FANG Diamondback Energy Inc. | Reduce -57.8% | 0.12% | −0.30 |
| RVMD Revolution Medicines Inc. | Reduce -61.4% | 0.37% | −0.27 |
| MASI Masimo Corp. | Sold out | 0.00% | −0.25 |
| ZS Zscaler Inc. | Sold out | 0.00% | −0.25 |
| HUBS HubSpot Inc. | Sold out | 0.00% | −0.24 |
| IBP Installed Building Products | Sold out | 0.00% | −0.23 |
| NXT Nextpower Inc. | Reduce -22.6% | 0.33% | −0.23 |
| MCO Moody's Corp. | Sold out | 0.00% | −0.23 |
| JBL Jabil Inc. | Reduce -61.4% | 0.17% | −0.22 |
| BLD Topbuild Corp. | Sold out | 0.00% | −0.22 |
| KKR KKR & Co. Inc. | Sold out | 0.00% | −0.22 |
| MSCI MSCI Inc. | Reduce -26.4% | 0.31% | −0.21 |
| BRZE Braze Inc. Class A | Reduce -34.1% | 0.19% | −0.21 |
| PRIM Primoris Services Corp. | Reduce -0.8% | 0.24% | −0.21 |
| COR Cencora Inc. | Reduce -8.4% | 0.37% | −0.21 |
| PH Parker Hannifin Corp. | Reduce -87.8% | 0.02% | −0.20 |
| TECH Bio-Techne Corp. | Sold out | 0.00% | −0.19 |
| FICO Fair Isaac Corp. | Sold out | 0.00% | −0.18 |
| BAC Bank of America Corp. | Reduce -77.5% | 0.04% | −0.17 |
| CRDO Credo Technology Group Holdi | Reduce -76.6% | 0.19% | −0.17 |
| IONQ Ionq Inc. | Sold out | 0.00% | −0.17 |
Portfolio Buys Q1 2026 → Q2 2026
| GOOGL Alphabet Inc. Class A | Add +85.0% | 4.38% | +1.93 |
| SNOW Snowflake Inc. | Add +141.6% | 1.44% | +0.99 |
| AXON Axon Enterprise Inc. | Add +40.2% | 2.73% | +0.84 |
| AMD Advanced Micro Devices | Add +7929.5% | 0.76% | +0.76 |
| MU Micron Technology Inc. | Add +127.2% | 0.86% | +0.72 |
| NVDA Nvidia Corp. | Add +27.9% | 5.28% | +0.66 |
| CRS Carpenter Technology | New | 0.63% | +0.63 |
| PTCT PTC Therapeutics Inc. | New | 0.52% | +0.52 |
| GILD Gilead Sciences Inc. | Add +4724.4% | 0.53% | +0.52 |
| CAT Caterpillar Inc. | Add +440.2% | 0.61% | +0.51 |
| AMAT Applied Materials Inc. | Add +21865.0% | 0.49% | +0.48 |
| LTH Life Time Group Holdings Inc. | Add +88.2% | 0.80% | +0.44 |
| LRCX Lam Research Corp. | New | 0.40% | +0.40 |
| ASML ASML Holding NV-NY Reg SHS | New | 0.37% | +0.37 |
| SNDK Sandisk Corp. | New | 0.36% | +0.36 |
| NPO Enpro Inc. | New | 0.35% | +0.35 |
| FROG Jfrog Ltd. | New | 0.33% | +0.33 |
| ANET Arista Networks Inc. | Add +68.8% | 0.73% | +0.33 |
| WWD Woodward Inc. | Add +93.4% | 0.73% | +0.32 |
| AVGO Broadcom Inc. | Add +25.8% | 1.92% | +0.31 |
| PANW Palo Alto Networks Inc. | Add +3.4% | 0.73% | +0.31 |
| GRMN Garmin Ltd. | Add +128.8% | 0.67% | +0.30 |
| MS Morgan Stanley | Add +89.4% | 0.64% | +0.30 |
| V Visa Inc. Class A | Add +67.0% | 0.85% | +0.28 |
| MAR Marriott International Class A | Add +160.4% | 0.48% | +0.27 |
| GH Guardant Health Inc. | Add +19.2% | 0.80% | +0.27 |
| C Citigroup Inc. | Add +1267.9% | 0.28% | +0.26 |
| TTMI TTM Technologies | New | 0.25% | +0.25 |
| FPS Forgent Power Solutions Class A | New | 0.25% | +0.25 |
| RBRK Rubrik Inc. Class A | New | 0.25% | +0.25 |
| SFM Sprouts Farmers Market Inc. | New | 0.24% | +0.24 |
| PRAX Praxis Precision Medicines I | Add +32966.2% | 0.24% | +0.24 |
| NUVL Nuvalent Inc. Class A | New | 0.24% | +0.24 |
| DY Dycom Industries Inc. | New | 0.23% | +0.23 |
| LLY Eli Lilly & Co. | Add +14.3% | 1.63% | +0.23 |
| MCHP Microchip Technology Inc. | Add +68.9% | 0.49% | +0.23 |
| TER Teradyne Inc. | New | 0.22% | +0.22 |
| ST Sensata Technologies Holdplc | New | 0.21% | +0.21 |
| BTSG Brightspring Health Services | New | 0.20% | +0.20 |
| RLAY Relay Therapeutics Inc. | New | 0.20% | +0.20 |
| CSX CSX Corp. | Add +90.2% | 0.49% | +0.20 |
| NET Cloudflare Inc. Class A | Add +54.3% | 0.67% | +0.20 |
| GEV GE Vernova Inc. | Add +21.1% | 0.93% | +0.20 |
| BLDR Builders Firstsource Inc. | New | 0.19% | +0.19 |
| PL Planet Labs PBC | Add +109.4% | 0.37% | +0.18 |
| RBLX Roblox Corp. Class A | New | 0.18% | +0.18 |
| PODD Insulet Corp. | Add +20870.1% | 0.18% | +0.17 |
| ARGX Argenx SE - ADR | New | 0.17% | +0.17 |
| MTZ Mastec Inc. | Add +49.8% | 0.51% | +0.17 |
| FLEX Flex Ltd. | New | 0.17% | +0.17 |
All Filings
| Quarter | Positions | 13F Reported Value | Top Holdings |
|---|---|---|---|
| Q2 2026 | 278 | $30.6B | NVDA, GOOGL, ASND, AXON, FTAI |
| Q1 2026 | 250 | $23.8B | NVDA, ASND, FIX, AAPL, FTAI |
| Q4 2025 | 241 | $24.0B | NVDA, ASND, AAPL, MSFT, GOOGL |
| Q3 2025 | 235 | $23.8B | NVDA, ASND, MSFT, AAPL, FIX |
| Q2 2025 | 239 | $23.8B | NVDA, ASND, MSFT, AAPL, AMZN |
| Q1 2025 | 244 | $20.5B | ASND, NVDA, AAPL, MSFT, AMZN |
| Q4 2024 | 239 | $23.0B | NVDA, AAPL, MSFT, ASND, AMZN |
| Q3 2024 | 247 | $22.1B | NVDA, AAPL, MSFT, ASND, AMZN |
| Q2 2024 | 248 | $20.4B | NVDA, MSFT, AAPL, ASND, AMZN |
| Q1 2024 | 244 | $19.0B | MSFT, ASND, AAPL, NVDA, AMZN |