WESTFIELD CAPITAL MANAGEMENT CO LP — 13F Holdings & Portfolio
CIK 1177719 · latest 13F-HR filed 2026-05-11
WESTFIELD CAPITAL MANAGEMENT CO LP manages $23.83B in 13F-reported U.S. long-equity assets across 250 reported positions as of its 2026-03-31 13F-HR filing. Its largest disclosed positions are NVDA (4.62%), ASND (4.62%), FIX (3.59%). Quarter over quarter (versus its 2025-12-31 filing) the fund opened 46 new positions, exited 37, added to 87, and trimmed 92.
AUM is the long-equity portion reported on Form 13F-HR. Excludes short positions, cash, foreign holdings, and non-13F assets. For informational purposes only — not investment advice.
$23.83B
Long-equity book
250
Distinct positions
2026-03-31
Filed 2026-05-11
+46 / −37 / ↑87 / ↓92
vs 2025-12-31
| Name | Title / Status | Ownership | Type |
|---|
Top Adds (vs prior quarter)
- FTAI AVIATION LTD$235.1M +50.8%
- COMFORT SYS USA INC$232.0M +37.2%
- INSMED INC$164.8M +219.0%
- VERTIV HOLDINGS CO$112.5M +30.5%
- MKS INC.$106.4M +79.3%
Top Trims
- MICROSOFT CORP-$173.5M -22.1%
- BANK AMERICA CORP-$158.3M -75.3%
- MASIMO CORP-$137.3M -69.3%
- META PLATFORMS INC-$131.1M -30.3%
- HEALTHEQUITY INC-$119.3M -66.7%
New Positions
- CHENIERE ENERGY INC$130.3M
- AMER SPORTS INC$129.6M
- AMERICAN INTL GROUP INC$109.8M
- JONES LANG LASALLE INC$105.8M
- ROSS STORES INC$102.2M
Exited Positions
- COMMVAULT SYS INC$132.5M
- ATLASSIAN CORPORATION$131.7M
- ADMA BIOLOGICS INC$127.6M
- ALKAMI TECHNOLOGY INC$95.0M
- ORACLE CORP$92.5M
Rows tagged Call or Put are options positions, not stock. Per SEC Form 13F-HR, Value shows the notional value of the underlying (shares covered × underlying price), not the option premium. Shares is the number of underlying shares covered (divide by 100 for contract count).
| # | Issuer | Symbol | CUSIP | Value | Weight | Shares | Type |
|---|---|---|---|---|---|---|---|
| 1 | NVIDIA CORPORATION | NVDA | 67066G104 | $1.10B | 4.62% | 6,317,039 | SH |
| 2 | ASCENDIS PHARMA A/S | ASND | 04351P101 | $1.10B | 4.62% | 4,813,440 | SH |
| 3 | COMFORT SYS USA INC | FIX | 199908104 | $856.2M | 3.59% | 620,915 | SH |
| 4 | APPLE INC | AAPL | 037833100 | $795.2M | 3.34% | 3,133,113 | SH |
| 5 | FTAI AVIATION LTD | FTAI | G3730V105 | $697.8M | 2.93% | 2,848,227 | SH |
| 6 | MICROSOFT CORP | MSFT | 594918104 | $610.6M | 2.56% | 1,649,513 | SH |
| 7 | ALPHABET INC | GOOGL | 02079K305 | $582.8M | 2.45% | 2,026,744 | SH |
| 8 | HOWMET AEROSPACE INC | HWM | 443201108 | $527.7M | 2.21% | 2,289,697 | SH |
| 9 | VERTIV HOLDINGS CO | VRT | 92537N108 | $481.5M | 2.02% | 1,921,696 | SH |
| 10 | AMAZON COM INC | AMZN | 023135106 | $474.8M | 1.99% | 2,279,654 | SH |
| 11 | AXON ENTERPRISE INC | AXON | 05464C101 | $451.9M | 1.90% | 1,064,134 | SH |
| 12 | BROADCOM INC | AVGO | 11135F101 | $382.8M | 1.61% | 1,236,925 | SH |
| 13 | ELI LILLY & CO | LLY | 532457108 | $335.3M | 1.41% | 364,579 | SH |
| 14 | TAPESTRY INC | TPR | 876030107 | $310.3M | 1.30% | 2,198,862 | SH |
| 15 | META PLATFORMS INC | META | 30303M102 | $301.4M | 1.26% | 526,822 | SH |
| 16 | LPL FINL HLDGS INC | LPLA | 50212V100 | $265.2M | 1.11% | 881,506 | SH |
| 17 | MKS INC. | MKSI | 55306N104 | $240.6M | 1.01% | 1,046,763 | SH |
| 18 | INSMED INC | INSM | 457669307 | $240.1M | 1.01% | 1,468,459 | SH |
| 19 | VAXCYTE INC | PCVX | 92243G108 | $211.9M | 0.89% | 3,646,138 | SH |
| 20 | ROCKET LAB CORP | RKLB | 773121108 | $203.7M | 0.85% | 3,172,611 | SH |
| 21 | NETFLIX INC. | NFLX | 64110L106 | $189.4M | 0.79% | 1,969,994 | SH |
| 22 | API GROUP CORP | APG | 00187Y100 | $187.8M | 0.79% | 4,634,929 | SH |
| 23 | QUANTA SVCS INC | PWR | 74762E102 | $182.2M | 0.76% | 331,816 | SH |
| 24 | GE VERNOVA INC | GEV | 36828A101 | $174.0M | 0.73% | 199,306 | SH |
| 25 | ARES MANAGEMENT CORPORATION | ARES | 03990B101 | $171.6M | 0.72% | 1,572,787 | SH |
| 26 | RHYTHM PHARMACEUTICALS INC | RYTM | 76243J105 | $167.8M | 0.70% | 1,929,123 | SH |
| 27 | TAIWAN SEMICONDUCTOR MANUFAC | TSM | 874039100 | $166.8M | 0.70% | 493,504 | SH |
| 28 | MARVELL TECHNOLOGY INC | MRVL | 573874104 | $165.7M | 0.70% | 1,673,381 | SH |
| 29 | BLOOM ENERGY CORP | BE | 093712107 | $161.4M | 0.68% | 1,191,572 | SH |
| 30 | SAMSARA INC | IOT | 79589L106 | $160.8M | 0.67% | 5,072,821 | SH |
| 31 | AMETEK INC | AME | 031100100 | $159.9M | 0.67% | 745,832 | SH |
| 32 | PERMIAN RESOURCES CORP | PR | 71424F105 | $159.5M | 0.67% | 7,481,457 | SH |
| 33 | DYNATRACE INC | DT | 268150109 | $155.7M | 0.65% | 4,209,594 | SH |
| 34 | REVOLUTION MEDICINES INC | RVMD | 76155X100 | $151.4M | 0.64% | 1,556,578 | SH |
| 35 | NATERA INC | NTRA | 632307104 | $150.9M | 0.63% | 754,729 | SH |
| 36 | FABRINET | FN | G3323L100 | $148.6M | 0.62% | 284,874 | SH |
| 37 | ABIVAX SA | ABVX | 00370M103 | $147.3M | 0.62% | 1,322,938 | SH |
| 38 | SERVICENOW INC | NOW | 81762P102 | $145.8M | 0.61% | 1,394,187 | SH |
| 39 | TECHNIPFMC PLC | FTI | G87110105 | $140.6M | 0.59% | 2,033,755 | SH |
| 40 | ROYAL CARIBBEAN GROUP | RCL | V7780T103 | $139.2M | 0.58% | 505,765 | SH |
| 41 | HILTON WORLDWIDE HLDGS INC | HLT | 43300A203 | $139.1M | 0.58% | 457,425 | SH |
| 42 | VISA INC | V | 92826C839 | $138.0M | 0.58% | 456,548 | SH |
| 43 | CENCORA INC | COR | 03073E105 | $137.3M | 0.58% | 436,909 | SH |
| 44 | ITT INC | ITT | 45073V108 | $134.0M | 0.56% | 703,309 | SH |
| 45 | CELSIUS HLDGS INC | CELH | 15118V207 | $133.7M | 0.56% | 3,768,911 | SH |
| 46 | NEXTPOWER INC | NXT | 65290E101 | $133.5M | 0.56% | 1,107,346 | SH |
| 47 | CHENIERE ENERGY INC | LNG | 16411R208 | $130.3M | 0.55% | 459,044 | SH |
| 48 | AMER SPORTS INC | AS | G0260P102 | $129.6M | 0.54% | 3,937,521 | SH |
| 49 | REGAL REXNORD CORPORATION | RRX | 758750103 | $127.7M | 0.54% | 681,717 | SH |
| 50 | MSCI INC | MSCI | 55354G100 | $126.0M | 0.53% | 233,764 | SH |
| Period | Filed | AUM | Holdings | Accession |
|---|---|---|---|---|
| 2026-03-31 | 2026-05-11 | $23.83B | 250 | 0001177719-26-000018 |
| 2025-12-31 | 2026-02-11 | $24.01B | 241 | 0001177719-26-000005 |
| 2025-09-30 | 2025-11-12 | $23.83B | 235 | 0001177719-25-000003 |