Institutional Manager · CIK 0001177719
WESTFIELD CAPITAL MANAGEMENT CO LP
BOSTON, MA · File #028-10220
Latest AUM
$24.01B
Positions
241
Top-10 Concentration
48.8%
Filings
9
Portfolio Value Over Time
2024-03
2024-06
2024-09
2024-12
2025-03
2025-06
2025-09
2025-12
Biggest QoQ Changes
Ranked by conviction flow (share change × current price) so mark-to-market moves don't dominate. Price effect column shows how much of the $ change was just the stock moving.
| Action | Issuer | Ticker / CUSIP | Δ Shares | Flow ($) | Price Effect |
|---|---|---|---|---|---|
| REDUCE | TRANSDIGM GROUP INC | TDG | -201,704 | -$268.2M | +$2.6M |
| EXITED | MERUS N V | N5749R100 | -2,132,489 | -$200.8M | $0 |
| ADD | SERVICENOW INC | NOW | +1,216,801 | +$186.4M | -$199.4M |
| REDUCE | COMFORT SYS USA INC | 199908104 | -164,360 | -$153.4M | +$90.1M |
| REDUCE | COHERENT CORP | COHR | -807,840 | -$149.1M | +$113.2M |
| NEW | ABIVAX SA | AAVXF | +1,009,966 | +$136.2M | $0 |
| NEW | API GROUP CORP | APG | +3,453,355 | +$132.1M | $0 |
| ADD | NETFLIX INC | NFLX | +1,366,899 | +$128.2M | -$254.9M |
| ADD | AMETEK INC | AME | +541,556 | +$111.2M | +$6.2M |
| NEW | DUTCH BROS INC | BROS | +1,779,616 | +$108.9M | $0 |
Sector Allocation
Filing History
- 13F HOLDINGS REPORTQ/E Dec 2025241 pos · $24.01B
- 13F HOLDINGS REPORTQ/E Sep 2025235 pos · $23.83B
- 13F HOLDINGS REPORTQ/E Jun 2025239 pos · $23.84B
- 13F HOLDINGS REPORTQ/E Mar 2025244 pos · $20.55B
- 13F HOLDINGS REPORTQ/E Dec 2024239 pos · $22.97B
- 13F HOLDINGS REPORTQ/E Sep 2024247 pos · $22.13B
- 13F HOLDINGS REPORTQ/E Jun 2024248 pos · $20.35B
- 13F HOLDINGS REPORTQ/E Mar 2024244 pos · $19.05B
- 13F HOLDINGS REPORTQ/E Dec 2023234 pos · $14.68B
Top 20 Holdings — Dec 2025
| # | Issuer | Ticker | Shares | Value | % of Portfolio |
|---|---|---|---|---|---|
| 1 | NVIDIA CORPORATION | NVDA | 5,951,049 | $1.11B | 7.60% |
| 2 | ASCENDIS PHARMA A/S | ASND | 5,185,696 | $1.11B | 7.58% |
| 3 | APPLE INC | AAPL | 3,274,318 | $890.2M | 6.10% |
| 4 | MICROSOFT CORP | MSFT | 1,621,219 | $784.1M | 5.37% |
| 5 | ALPHABET INC | GOOG | 2,178,478 | $681.9M | 4.67% |
| 6 | COMFORT SYS USA INC | 199908104 | 668,835 | $624.2M | 4.28% |
| 7 | AMAZON COM INC | AMZN | 2,330,770 | $538.0M | 3.69% |
| 8 | AXON ENTERPRISE INC | AXON | 831,177 | $472.1M | 3.23% |
| 9 | FTAI AVIATION LTD | FTAIN | 2,350,625 | $462.7M | 3.17% |
| 10 | HOWMET AEROSPACE INC | HWM | 2,219,125 | $455.0M | 3.12% |
| 11 | META PLATFORMS INC | META | 655,283 | $432.5M | 2.96% |
| 12 | BROADCOM INC | AVGO | 1,112,318 | $385.0M | 2.64% |
| 13 | VERTIV HOLDINGS CO | VRT | 2,277,716 | $369.0M | 2.53% |
| 14 | ELI LILLY & CO | LLY | 277,549 | $298.3M | 2.04% |
| 15 | TAPESTRY INC | TPR | 2,098,104 | $268.1M | 1.84% |
| 16 | REVOLUTION MEDICINES INC | RVMDW | 2,845,013 | $226.6M | 1.55% |
| 17 | SERVICENOW INC | NOW | 1,476,803 | $226.2M | 1.55% |
| 18 | LPL FINL HLDGS INC | 50212V100 | 625,562 | $223.4M | 1.53% |
| 19 | VISA INC | V | 603,926 | $211.8M | 1.45% |
| 20 | BANK AMERICA CORP | 060505104 | 3,823,609 | $210.3M | 1.44% |