WESTFIELD CAPITAL MANAGEMENT CO LP
Long book
$23.83B
Q1 2026
Positions
250
Top-10 weight
30%
concentration
Last quarter
+20.3%
SPY +14.8%
Turnover
29%
of book per quarter
Strategy in plain words
auto-generated from filingsWESTFIELD CAPITAL MANAGEMENT CO LP is an institutional manager, running a $23.83B US long book across 250 positions.
The portfolio is moderately concentrated (top 10 ≈ 30% of the book). The portfolio is actively managed, with meaningful quarterly turnover. Current anchor positions: NVIDIA CORP, The Bank of New York Mellon Corporation, COMFORT SYSTEMS USA INC, APPLE INC, FTAI AVIATION LTD.
Over the last 9 quarters its long book ran on average 0.1pp per quarter behind the S&P 500, beating the index in 5 of 9 quarters. Signal value of individual moves is limited — treat changes as weak evidence.
Implied long-book return vs S&P 500
methodology: positions priced quarterly, no shorts/options Fund long book S&P 500
Q1 2024
-2.2%
Q2 2024
+6.4%
Q3 2024
+4.6%
Q4 2024
-11.3%
Q1 2025
+18.2%
Q2 2025
+5.2%
Q3 2025
+1.7%
Q4 2025
-3.5%
Q1 2026
+20.3%
Sector allocation
Technology 35%
Industrials 21%
Services media 10%
Healthcare 9%
Financials 8%
Consumer discretionary 6%
Other 5%
Utilities 2%
Long book by quarter
What does WESTFIELD CAPITAL own?
Q1 2026 13F| Company | Sector | Shares | Value | % of book | Change |
|---|---|---|---|---|---|
| NVDA NVIDIA CORP | Technology | 6.3M | $1.10B | 4.6% | +6.2% |
| FIX COMFORT SYSTEMS USA INC | Industrials | 620.9K | $856.2M | 3.6% | -7.2% |
| AAPL APPLE INC | Technology | 3.1M | $795.2M | 3.3% | -4.3% |
| FTAI FTAI AVIATION LTD | Services media | 2.8M | $697.8M | 2.9% | +21.2% |
| MSFT MICROSOFT CORP | Technology | 1.6M | $610.6M | 2.6% | +1.7% |
| GOOGL ALPHABET INC-CL A | Technology | 2.0M | $582.8M | 2.4% | -7.0% |
| HWM HOWMET AEROSPACE INC | Industrials | 2.3M | $527.7M | 2.2% | +3.2% |
| VRT VERTIV HOLDINGS CO-A | Technology | 1.9M | $481.5M | 2.0% | -15.6% |
| AMZN AMAZON.COM INC | Consumer discretionary | 2.3M | $474.8M | 2.0% | -2.2% |
| AXON AXON ENTERPRISE INC | Industrials | 1.1M | $451.9M | 1.9% | +28.0% |
| AVGO BROADCOM INC | Technology | 1.2M | $382.8M | 1.6% | +11.2% |
| LLY ELI LILLY & CO | Healthcare | 364.6K | $335.3M | 1.4% | +31.4% |
| TPR TAPESTRY INC | Other | 2.2M | $310.3M | 1.3% | +4.8% |
| META META PLATFORMS INC-CLASS A | Technology | 526.8K | $301.4M | 1.3% | -19.6% |
| LPLA LPL FINANCIAL HOLDINGS INC | Financials | 881.5K | $265.2M | 1.1% | +40.9% |
| MKSI MKS INC | Technology | 1.0M | $240.6M | 1.0% | +24.6% |
| INSM INSMED INC | Healthcare | 1.5M | $240.1M | 1.0% | +239.5% |
| PCVX VAXCYTE INC | Healthcare | 3.6M | $211.9M | 0.9% | +3.0% |
| RKLB ROCKET LAB CORP | Industrials | 3.2M | $203.7M | 0.9% | +22.4% |
| NFLX NETFLIX INC | Services media | 2.0M | $189.4M | 0.8% | +23.3% |
| APG API GROUP CORP | Services media | 4.6M | $187.8M | 0.8% | +34.2% |
| PWR QUANTA SERVICES INC | Industrials | 331.8K | $182.2M | 0.8% | +21.3% |
| GEV GE VERNOVA INC | Industrials | 199.3K | $174.0M | 0.7% | +12.0% |
| ARES ARES MANAGEMENT CORP - A | Financials | 1.6M | $171.6M | 0.7% | +36.6% |
| RYTM RHYTHM PHARMACEUTICALS INC | Healthcare | 1.9M | $167.8M | 0.7% | +52.2% |
| MRVL MARVELL TECHNOLOGY INC | Technology | 1.7M | $165.7M | 0.7% | -14.1% |
| BE BLOOM ENERGY CORP- A | Industrials | 1.2M | $161.4M | 0.7% | +4.0% |
| IOT SAMSARA INC-CL A | Technology | 5.1M | $160.8M | 0.7% | +28.3% |
| AME AMETEK INC | Technology | 745.8K | $159.9M | 0.7% | -17.1% |
| PR PERMIAN RESOURCES CORP-CL A | Energy | 7.5M | $159.5M | 0.7% | +25.7% |
| DT DYNATRACE INC | Technology | 4.2M | $155.7M | 0.7% | +25.4% |
| RVMD REVOLUTION MEDICINES INC | Healthcare | 1.6M | $151.4M | 0.6% | -45.3% |
| NTRA NATERA INC | Healthcare | 754.7K | $150.9M | 0.6% | +5.6% |
| FN FABRINET | Technology | 284.9K | $148.6M | 0.6% | +49.8% |
| NOW SERVICENOW INC | Technology | 1.4M | $145.8M | 0.6% | -5.6% |
| FTI TECHNIPFMC PLC | Industrials | 2.0M | $140.6M | 0.6% | +4.2% |
| RCL ROYAL CARIBBEAN CRUISES LTD | Industrials | 505.8K | $139.2M | 0.6% | +12.7% |
| HLT HILTON WORLDWIDE HOLDINGS IN | Services media | 457.4K | $139.1M | 0.6% | +27.9% |
| V VISA INC-CLASS A SHARES | Services media | 456.5K | $138.0M | 0.6% | -24.4% |
| COR CENCORA INC | Consumer discretionary | 436.9K | $137.3M | 0.6% | +36.9% |
| ITT ITT INC | Industrials | 703.3K | $134.0M | 0.6% | +19.7% |
| CELH CELSIUS HOLDINGS INC | Consumer staples | 3.8M | $133.7M | 0.6% | +144.1% |
| NXT NEXTPOWER INC-CL A | Technology | 1.1M | $133.5M | 0.6% | +1.6% |
| LNG CHENIERE ENERGY INC | Utilities | 459.0K | $130.3M | 0.5% | New |
| AS AMER SPORTS INC | Other | 3.9M | $129.6M | 0.5% | New |
| RRX REGAL REXNORD CORP | Industrials | 681.7K | $127.7M | 0.5% | -23.7% |
| MSCI MSCI INC | Services media | 233.8K | $126.0M | 0.5% | +12.5% |
| GH GUARDANT HEALTH INC | Healthcare | 1.4M | $125.9M | 0.5% | +152.7% |
| LYV LIVE NATION ENTERTAINMENT IN | Services media | 810.7K | $123.6M | 0.5% | +4.6% |
| TSLA TESLA INC | Industrials | 316.1K | $117.5M | 0.5% | -31.5% |
13F filing history
| Period | Form | Filed | Entries | Reported value | Flags | Source |
|---|---|---|---|---|---|---|
| Q1 2026 | 13F-HR | May 11, 2026 | 250 | $23.83B | canonical | SEC ↗ |
| Q4 2025 | 13F-HR | Feb 11, 2026 | 241 | $24.01B | canonical | SEC ↗ |
| Q3 2025 | 13F-HR | Nov 12, 2025 | 235 | $23.83B | canonical | SEC ↗ |
| Q2 2025 | 13F-HR | Aug 12, 2025 | 239 | $23.84B | canonical | SEC ↗ |
| Q1 2025 | 13F-HR | May 9, 2025 | 244 | $20.55B | canonical | SEC ↗ |
| Q4 2024 | 13F-HR | Feb 11, 2025 | 239 | $22.97B | canonical | SEC ↗ |
| Q3 2024 | 13F-HR | Nov 12, 2024 | 247 | $22.13B | canonical | SEC ↗ |
| Q2 2024 | 13F-HR | Aug 14, 2024 | 248 | $20.35B | canonical | SEC ↗ |
| Q1 2024 | 13F-HR | May 10, 2024 | 244 | $19.05B | canonical | SEC ↗ |
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