CIK: 0001177719
Total reported value
$23.8B
Reporting period: 2026-03-31 · Number of holdings: 250
WESTFIELD CAPITAL MANAGEMENT CO LP disclosed 250 holdings in its latest 13F filing for the period ending 2026-03-31, with total reported value of $23.8B and a quarterly turnover rate of 40.6%.
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Westfield Capital Management Co LP's disclosed holdings carry a Herfindahl concentration index of 0.014 — mathematically equivalent to about 70 equally-sized positions, well below its 250 actual disclosed holdings. That gap points to a strategy built around a small core of high-conviction bets rather than broad diversification.
Position sizes vary widely across the portfolio (a coefficient of variation of 1.60), with a handful of outsized bets alongside many smaller positions.
No strong tilt toward either adding to existing winners or initiating outsized new positions was observed in the latest reported quarter.
Add FTAI
+21.2% $235.1M
Add FIX
-7.2% $232.0M
Trim MSFT
+1.7% -$173.5M
Add INSM
+239.5% $164.8M
Trim BAC
-72.1% -$158.3M
Trim MASI*
-77.6% -$137.3M
Westfield is aggressively rotating capital from Financials into IT and Industrials while maintaining a strict, high-diversification mandate. The manager bought the dip on quality tech leaders like MSFT, accelerated momentum bets on FTAI and INSM, and cleanly exited lower-conviction positions such as CVLT and TEAM, signaling a definitive shift toward cyclical tech exposure.
The embedded bet is a sustained industrial capex cycle fueling AI infrastructure buildouts, favoring hardware and specialized manufacturing over rate-sensitive financials. The opposing thesis argues that IT exposure at 31.7% creates a liquidity trap if earnings growth stalls, leaving the fund vulnerable to a sharp multiple compression in mega-cap tech.
With 250 names and an HHI of 0.014, portfolio impact is structurally diluted by fragmentation. The real vulnerability is not concentration risk—it’s the hidden drag from low-conviction tails that consume capital when position sizing discipline forces uniform weighting across a shallow opportunity set during a positioning squeeze.
Sourced and summarized by AI from public SEC filings, limited to historical activity. Not investment guidance.
Showing top 200 holdings (of 250 total)
| # | Ticker | Issuer | Asset Subclass | Weight | Weight Change | Shares Change | 4Q Trend |
|---|---|---|---|---|---|---|---|
| 1 | NVDA | Nvidia CORP | Stock-Tech | 4.62% | — | +6.15% | |
| 2 | ASND | Ascendis Pharma A/S | Stock-Other | 4.62% | — | -7.18% | |
| 3 | FIX | Comfort Systems USA INC | Stock-Industrials | 3.59% | +0.99% | -7.16% | |
| 4 | AAPL | Apple INC | Stock-Tech | 3.34% | -0.37% | -4.31% | |
| 5 | FTAI | FTAI Aviation Ltd. | Stock-Industrials | 2.93% | +1.00% | +21.17% | |
| 6 | MSFT | Microsoft CORP | Stock-Tech | 2.56% | -0.71% | +1.75% | |
| 7 | GOOGL | Alphabet Inc-cl A | Stock-Comm Services | 2.45% | -0.39% | -6.97% | |
| 8 | HWM | Howmet Aerospace INC | Stock-Industrials | 2.21% | +0.31% | +3.18% | |
| 9 | VRT | Vertiv Holdings Co-a | Stock-Industrials | 2.02% | +0.48% | -15.63% | |
| 10 | AMZN | Amazon.com INC | Stock-Consumer Disc | 1.99% | — | -2.19% | |
| 11 | AXON | Axon Enterprise INC | Stock-Industrials | 1.90% | — | +28.03% | |
| 12 | AVGO | Broadcom INC | Stock-Tech | 1.61% | — | +11.20% | |
| 13 | LLY | Eli Lilly & Co | Stock-Healthcare | 1.41% | — | +31.36% | |
| 14 | TPR | Tapestry INC | Stock-Consumer Disc | 1.30% | — | +4.80% | |
| 15 | META | Meta Platforms Inc-class A | Stock-Comm Services | 1.26% | -0.54% | -19.60% | |
| 16 | LPLA | Lpl Financial Holdings INC | Stock-Financials | 1.11% | — | +40.91% | |
| 17 | MKSI | Mks INC | Stock-Tech | 1.01% | +0.45% | +24.65% | |
| 18 | INSM | Insmed INC | Stock-Healthcare | 1.01% | +0.70% | +239.51% | |
| 19 | PCVX | Vaxcyte INC | Stock-Other | 0.89% | — | +3.01% | |
| 20 | RKLB | Rocket Lab CORP | Stock-Industrials | 0.85% | — | +22.38% | |
| 21 | NFLX | Netflix INC | Stock-Comm Services | 0.79% | — | +23.31% | |
| 22 | APG | Api Group CORP | Stock-Industrials | 0.79% | — | +34.22% | |
| 23 | PWR | Quanta Services INC | Stock-Industrials | 0.76% | — | +21.31% | |
| 24 | GEV | GE Vernova INC | Stock-Industrials | 0.73% | — | +12.01% | |
| 25 | ARES | Ares Management CORP - A | Stock-Financials | 0.72% | — | +36.62% | |
| 26 | RYTM | Rhythm Pharmaceuticals INC | Stock-Other | 0.70% | — | +52.24% | |
| 27 | TSM | Taiwan Semiconductor-sp Adr | Stock-Tech | 0.70% | — | +10.60% | |
| 28 | MRVL | Marvell Technology INC | Stock-Tech | 0.70% | — | -14.09% | |
| 29 | BE | Bloom Energy Corp- A | Stock-Industrials | 0.68% | — | +4.04% | |
| 30 | IOT | Samsara Inc-cl A | Stock-Tech | 0.67% | — | +28.30% | |
| 31 | AME | Ametek INC | Stock-Industrials | 0.67% | — | -17.15% | |
| 32 | PR | Permian Resources Corp-cl A | Stock-Energy | 0.67% | +0.32% | +25.71% | |
| 33 | DT | Dynatrace INC | Stock-Tech | 0.65% | — | +25.41% | |
| 34 | RVMD | Revolution Medicines INC | Stock-Healthcare | 0.64% | -0.30% | -45.29% | |
| 35 | NTRA | Natera INC | Stock-Healthcare | 0.63% | — | +5.60% | |
| 36 | FN | Fabrinet | Stock-Tech | 0.62% | — | +49.80% | |
| 37 | ABVX | Abivax Sa-adr | Stock-Other | 0.62% | — | +30.99% | |
| 38 | NOW | Servicenow INC | Stock-Tech | 0.61% | -0.33% | -5.59% | |
| 39 | FTI | TechnipFMC plc | Stock-Energy | 0.59% | — | +4.17% | |
| 40 | RCL | Royal Caribbean Cruises Ltd. | Stock-Consumer Disc | 0.58% | — | +12.73% | |
| 41 | HLT | Hilton Worldwide Holdings In | Stock-Consumer Disc | 0.58% | — | +27.87% | |
| 42 | V | Visa Inc-class A Shares | Stock-Financials | 0.58% | -0.30% | -24.40% | |
| 43 | COR | Cencora INC | Stock-Healthcare | 0.58% | — | +36.87% | |
| 44 | ITT | Itt INC | Stock-Industrials | 0.56% | — | +19.72% | |
| 45 | CELH | Celsius Holdings INC | Stock-Consumer Staples | 0.56% | — | +144.07% | |
| 46 | NXT | Nextpower Inc-cl A | Stock-Tech | 0.56% | — | +1.56% | |
| 47 | LNG | Cheniere Energy INC | Stock-Energy | 0.55% | +0.55% | NEW | |
| 48 | AS | Amer Sports, Inc. | Stock-Consumer Disc | 0.54% | +0.54% | NEW | |
| 49 | RRX | Regal Rexnord CORP | Stock-Industrials | 0.54% | — | -23.67% | |
| 50 | MSCI | Msci INC | Stock-Financials | 0.53% | — | +12.50% |
Performance for Q3 2026
+1.9%
Performance Last 4 Quarters
+28%
Based on 80% of reported portfolio value with available pricing
| Period | Holdings | Total value | Stability | Top holdings |
|---|---|---|---|---|
| 2026-03-31 | 250 | $23.8B | 41 | |
| 2025-12-31 | 241 | $24.0B | 34 | |
| 2025-09-30 | 235 | $23.8B | 59 | |
| 2025-06-30 | 239 | $23.8B | 0 | |
| 2025-03-31 | 244 | $20.5B | 100 | |
| 2024-12-31 | 239 | $23.0B | 0 | |
| 2024-09-30 | 247 | $22.1B | 0 | |
| 2024-06-30 | 248 | $20.4B | 0 | |
| 2024-03-31 | 244 | $19.0B | 0 | |
| 2023-12-31 | 239 | $17.2B | 0 | |
| 2023-09-30 | 234 | $14.7B | 0 | |
| 2023-06-30 | 227 | $15.7B | 0 | |
| 2023-03-31 | 222 | $14.2B | 0 | |
| 2022-12-31 | 226 | $13.0B | 0 | |
| 2022-09-30 | 230 | $12.6B | 0 | |
| 2022-06-30 | 235 | $12.7B | 0 | |
| 2022-03-31 | 235 | $15.6B | 0 | |
| 2021-12-31 | 244 | $16.8B | 0 | |
| 2021-09-30 | 235 | $16.6B | 0 | |
| 2021-06-30 | 241 | $16.7B | 100 | |
| 2021-03-31 | 243 | $16.1B | 41 | |
| 2020-12-31 | 247 | $16.9B | 34 | |
| 2020-09-30 | 235 | $15.4B | 32 | |
| 2020-06-30 | 230 | $14.5B | 42 | |
| 2020-03-31 | 216 | $11.4B | 50 | |
| 2019-12-31 | 231 | $14.0B | 37 | |
| 2019-09-30 | 234 | $12.5B | 43 | |
| 2019-06-30 | 243 | $13.3B | 31 | |
| 2019-03-31 | 246 | $13.1B | 32 | |
| 2018-12-31 | 240 | $11.7B | 45 | |
| 2018-09-30 | 249 | $14.2B | 35 | |
| 2018-06-30 | 243 | $13.4B | 35 | |
| 2018-03-31 | 248 | $13.0B | 33 | |
| 2017-12-31 | 244 | $13.1B | 32 | |
| 2017-09-30 | 251 | $13.0B | 34 | |
| 2017-06-30 | 249 | $11.7B | 35 | |
| 2017-03-31 | 258 | $11.6B | 40 | |
| 2016-12-31 | 253 | $11.4B | 41 | |
| 2016-09-30 | 249 | $12.4B | 38 | |
| 2016-06-30 | 257 | $12.1B | 39 | |
| 2016-03-31 | 252 | $13.1B | 50 | |
| 2015-12-31 | 272 | $14.9B | 47 | |
| 2015-09-30 | 262 | $14.1B | 44 | |
| 2015-06-30 | 283 | $16.4B | 40 | |
| 2015-03-31 | 302 | $17.4B | 38 | |
| 2014-12-31 | 313 | $17.0B | 33 | |
| 2014-09-30 | 300 | $16.4B | 29 | |
| 2014-06-30 | 313 | $16.8B | 33 | |
| 2014-03-31 | 324 | $16.7B | 33 | |
| 2013-12-31 | 324 | $17.0B | 39 | |
| 2013-09-30 | 346 | $15.6B | 32 | |
| 2013-06-30 | 358 | $14.5B | — |
Westfield Capital Management Co LP's most significant position changes for 2026-03-31: Sold out: Commvault Systems INC (CVLT); Sold out: Atlassian Corp-cl A (TEAM); New buy: Cheniere Energy INC (LNG); New buy: Amer Sports, Inc. (AS); Sold out: Adma Biologics INC (ADMA).
| # | Ticker | Issuer | Weight Change | Shares Change | Action |
|---|---|---|---|---|---|
| 1 | FTAI | FTAI Aviation Ltd. | +1% | +21.17% | Add |
| 2 | FIX | Comfort Systems USA INC | +1% | -7.16% | Trim |
| 3 | INSM | Insmed INC | +0.7% | +239.51% | Add |
| 4 | VRT | Vertiv Holdings Co-a | +0.5% | -15.63% | Trim |
| 5 | MKSI | Mks INC | +0.5% | +24.65% | Add |
| 6 | PLXS | Plexus CORP | +0.3% | +7294.10% | Add |
| 7 | PR | Permian Resources Corp-cl A | +0.3% | +25.71% | Add |
| 8 | HWM | Howmet Aerospace INC | +0.3% | +3.18% | Add |
| 9 | PLTR | Palantir Technologies Inc-a | +0.3% | +336.37% | Add |
| 10 | RVMD | Revolution Medicines INC | -0.3% | -45.29% | Trim |
| 11 | V | Visa Inc-class A Shares | -0.3% | -24.40% | Trim |
| 12 | AZO | Autozone INC | -0.3% | -44.52% | Trim |
| 13 | UNH | Unitedhealth Group INC | -0.3% | -98.80% | Trim |
| 14 | NOW | Servicenow INC | -0.3% | -5.59% | Trim |
| 15 | SMTC | Semtech CORP | -0.3% | -47.70% | Trim |
| 16 | HUBS | Hubspot INC | -0.4% | -33.84% | Trim |
| 17 | AAPL | Apple INC | -0.4% | -4.31% | Trim |
| 18 | TSLA | Tesla INC | -0.4% | -31.53% | Trim |
| 19 | GOOGL | Alphabet Inc-cl A | -0.4% | -6.97% | Trim |
| 20 | DXCM | Dexcom INC | -0.4% | -98.12% | Trim |
| 21 | ABBV | Abbvie INC | -0.4% | -97.47% | Trim |
| 22 | HEI-A | Heico Corp-class A | -0.4% | -95.11% | Trim |
| 23 | CWST | Casella Waste Systems Inc-a | -0.4% | -50.61% | Trim |
| 24 | PODD | Insulet CORP | -0.5% | -99.56% | Trim |
| 25 | HQY | Healthequity INC | -0.5% | -63.49% | Trim |
| 26 | META | Meta Platforms Inc-class A | -0.5% | -19.60% | Trim |
| 27 | MASI* | Masimo CORP | -0.6% | -77.58% | Trim |
| 28 | BAC | Bank Of America CORP | -0.7% | -72.10% | Trim |
| 29 | MSFT | Microsoft CORP | -0.7% | +1.75% | Add |
| 30 | CVLT | Commvault Systems INC | — | EXIT | Sold out |
| 31 | TEAM | Atlassian Corp-cl A | — | EXIT | Sold out |
| 32 | LNG | Cheniere Energy INC | — | NEW | New buy |
| 33 | AS | Amer Sports, Inc. | — | NEW | New buy |
| 34 | ADMA | Adma Biologics INC | — | EXIT | Sold out |
| 35 | AIG | American International Group | — | NEW | New buy |
| 36 | JLL | Jones Lang Lasalle INC | — | NEW | New buy |
| 37 | ROST | Ross Stores INC | — | NEW | New buy |
| 38 | WWD | Woodward INC | — | NEW | New buy |
| 39 | ANET | Arista Networks INC | — | NEW | New buy |
| 40 | ALKT | Alkami Technology INC | — | EXIT | Sold out |
| 41 | ORCL | Oracle CORP | — | EXIT | Sold out |
| 42 | BURL | Burlington Stores INC | — | EXIT | Sold out |
| 43 | LTH | Life Time Group Holdings INC | — | NEW | New buy |
| 44 | DKNG | Draftkings Inc-cl A | — | EXIT | Sold out |
| 45 | MS | Morgan Stanley | — | NEW | New buy |
| 46 | MTZ | Mastec INC | — | NEW | New buy |
| 47 | TRU | Transunion | — | EXIT | Sold out |
| 48 | GWRE | Guidewire Software INC | — | NEW | New buy |
| 49 | VMC | Vulcan Materials Co | — | EXIT | Sold out |
| 50 | SLAB | Silicon Laboratories INC | — | EXIT | Sold out |
| Period | Filed | Type | EDGAR |
|---|---|---|---|
| 2026-03-31 | 2026-05-11 | 13F-HR | View on EDGAR |
| 2025-12-31 | 2026-02-11 | 13F-HR | View on EDGAR |
| 2025-09-30 | 2025-11-12 | 13F-HR | View on EDGAR |
| 2025-06-30 | 2025-08-12 | 13F-HR | View on EDGAR |
| 2025-03-31 | 2025-05-09 | 13F-HR | View on EDGAR |
| 2024-12-31 | 2025-02-11 | 13F-HR | View on EDGAR |
| 2024-09-30 | 2024-11-12 | 13F-HR | View on EDGAR |
| 2024-06-30 | 2024-08-14 | 13F-HR | View on EDGAR |
| 2024-03-31 | 2024-05-10 | 13F-HR | View on EDGAR |
| 2023-12-31 | 2024-02-09 | 13F-HR | View on EDGAR |
| 2023-09-30 | 2023-11-13 | 13F-HR | View on EDGAR |
| 2023-06-30 | 2023-08-11 | 13F-HR | View on EDGAR |
| 2023-03-31 | 2023-05-12 | 13F-HR | View on EDGAR |
| 2022-12-31 | 2023-02-13 | 13F-HR | View on EDGAR |
| 2022-09-30 | 2022-11-14 | 13F-HR | View on EDGAR |
| 2022-06-30 | 2022-08-12 | 13F-HR | View on EDGAR |
| 2022-03-31 | 2022-05-16 | 13F-HR | View on EDGAR |
| 2021-12-31 | 2022-02-10 | 13F-HR | View on EDGAR |
| 2021-09-30 | 2021-11-12 | 13F-HR | View on EDGAR |
| 2021-06-30 | 2021-08-10 | 13F-HR | View on EDGAR |
| 2021-03-31 | 2021-05-14 | 13F-HR | View on EDGAR |
| 2020-12-31 | 2021-02-12 | 13F-HR | View on EDGAR |
| 2020-09-30 | 2020-11-13 | 13F-HR | View on EDGAR |
| 2020-06-30 | 2020-08-13 | 13F-HR | View on EDGAR |
| 2020-03-31 | 2020-05-14 | 13F-HR | View on EDGAR |
| 2019-12-31 | 2020-02-13 | 13F-HR | View on EDGAR |
| 2019-09-30 | 2019-11-08 | 13F-HR | View on EDGAR |
| 2019-06-30 | 2019-08-13 | 13F-HR | View on EDGAR |
| 2019-03-31 | 2019-05-14 | 13F-HR | View on EDGAR |
| 2018-12-31 | 2019-02-08 | 13F-HR | View on EDGAR |
| 2018-09-30 | 2018-11-14 | 13F-HR | View on EDGAR |
| 2018-06-30 | 2018-08-13 | 13F-HR | View on EDGAR |
| 2018-03-31 | 2018-05-14 | 13F-HR | View on EDGAR |
| 2017-12-31 | 2018-02-13 | 13F-HR | View on EDGAR |
| 2017-09-30 | 2017-11-13 | 13F-HR | View on EDGAR |
| 2017-06-30 | 2017-08-11 | 13F-HR | View on EDGAR |
| 2017-03-31 | 2017-05-12 | 13F-HR | View on EDGAR |
| 2016-12-31 | 2017-02-10 | 13F-HR | View on EDGAR |
| 2016-09-30 | 2016-11-10 | 13F-HR | View on EDGAR |
| 2016-06-30 | 2016-08-12 | 13F-HR | View on EDGAR |
| 2016-03-31 | 2016-05-13 | 13F-HR | View on EDGAR |
| 2015-12-31 | 2016-02-11 | 13F-HR | View on EDGAR |
| 2015-09-30 | 2015-11-12 | 13F-HR | View on EDGAR |
| 2015-06-30 | 2015-08-13 | 13F-HR | View on EDGAR |
| 2015-03-31 | 2015-05-13 | 13F-HR | View on EDGAR |
| 2014-12-31 | 2015-02-13 | 13F-HR | View on EDGAR |
| 2014-09-30 | 2014-11-12 | 13F-HR | View on EDGAR |
| 2014-06-30 | 2014-08-13 | 13F-HR | View on EDGAR |
| 2014-03-31 | 2014-05-12 | 13F-HR | View on EDGAR |
| 2013-12-31 | 2014-02-07 | 13F-HR | View on EDGAR |
| 2013-09-30 | 2013-11-12 | 13F-HR | View on EDGAR |
| 2013-06-30 | 2013-08-09 | 13F-HR | View on EDGAR |
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