WESTFIELD CAPITAL MANAGEMENT CO LP
Q2 2023 Form 13-F

BOSTON, MASSACHUSETTS
CIK 0001177719 · CRD 146990 · SEC-registered investment adviser
$15.7B Reported Value Total

WESTFIELD CAPITAL MANAGEMENT COMPANY, L.P. reports 759 total accounts under management (AUM). There are 759 discretionary accounts valued at $13,315,528,816, and 0 non-discretionary accounts.

Source: Form ADV filed * Note that certain holdings are exempt from Form 13-F reporting, so the AUM totals may be greater than the Form 13-F total.
SEC Registered Discretionary Manager
Firm Brochure (Part 2A) Client Relationship Summary (Form CRS)
Private funds (Form ADV)
11 funds · $185.4M gross asset value
Other: $68.8M · Hedge Fund: $34.8M · Private Equity Fund: $128.8K
Source: Form ADV filed 2026-07-01
Reported value
$15.7B
Quarter over quarter
+8.7%
Holdings
227
Top-10 concentration
21.8%

Filing Structure

Reports holdings for

Holdings reported by

Key People

Form ADV owners & control persons
William Albert Muggia
MEMBER OF MANAGEMENT COMMITTEE
Kathryn Ann Kearney
PARTNER, CHIEF FINANCIAL OFFICER AND CHIEF COMPLIANCE OFFICER
Richard Dailyong Lee
CHIEF INVESTMENT OFFICER
Q1 2023
Q3 2023
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Coverage begins with the second quarter of 2013. Earlier quarters are not shown while their accuracy is being verified.

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Q2 2023 13F filing summary

Period of report June 30, 2023
Filed August 11, 2023
Form 13F-HR
Reported value $15.7B
Positions 227
Change in reported value +11.2%
New positions 32
Exited positions 27
Position turnover 23.2%
Top-10 concentration 21.8%

13F filings by quarter

Quarter Positions Value
Q2 2026 13F
Filed Aug 12, 2026
 278 $30.6B
Q1 2026 13F
Filed May 11, 2026
 250 $23.8B
Q4 2025 13F
Filed Feb 11, 2026
 241 $24.0B
Q3 2025 13F
Filed Nov 12, 2025
 235 $23.8B
Q2 2025 13F
Filed Aug 12, 2025
 239 $23.8B
Q1 2025 13F
Filed May 9, 2025
 244 $20.5B
Q4 2024 13F
Filed Feb 11, 2025
 239 $23.0B
Q3 2024 13F
Filed Nov 12, 2024
 247 $22.1B
Q2 2024 13F
Filed Aug 14, 2024
 248 $20.4B
Q1 2024 13F
Filed May 10, 2024
 244 $19.0B
Q4 2023 13F
Filed Feb 9, 2024
 239 $17.2B
Q3 2023 13F
Filed Nov 13, 2023
 234 $14.7B
Q2 2023 13F
Filed Aug 11, 2023
 227 $15.7B
Q1 2023 13F
Filed May 12, 2023
 222 $14.2B
Q4 2022 13F
Filed Feb 13, 2023
 226 $13.0B
Q3 2022 13F
Filed Nov 14, 2022
 230 $12.6B
Q2 2022 13F
Filed Aug 12, 2022
 235 $12.7B
Q1 2022 13F
Filed May 16, 2022
 235 $15.6B
Q4 2021 13F
Filed Feb 10, 2022
 244 $16.8B
Q3 2021 13F
Filed Nov 12, 2021
 235 $16.6B

33 earlier quarters on file — choose one from the quarter menu above.

Top 20 holdings · Q2 2023

# Holding Reported value % of portfolio
1 AAPL APPLE INC $532.6M 3.38%
2 MSFT MICROSOFT CORP $470.5M 2.99%
3 GOOGL ALPHABET INC $405.7M 2.58%
4 ICLR ICON PLC $344.6M 2.19%
5 TDG TRANSDIGM GROUP INC $325.3M 2.07%
6 ASND ASCENDIS PHARMA A/S $324.1M 2.06%
7 AMZN AMAZON COM INC $315.2M 2.0%
8 V VISA INC $259.1M 1.65%
9 NVDA NVIDIA CORPORATION $225.8M 1.43%
10 BLDR BUILDERS FIRSTSOURCE INC $223.4M 1.42%
11 FTNT FORTINET INC $215.9M 1.37%
12 META META PLATFORMS INC $207.9M 1.32%
13 UNH UNITEDHEALTH GROUP INC $204.6M 1.3%
14 CMG CHIPOTLE MEXICAN GRILL INC $196.4M 1.25%
15 LLY LILLY ELI & CO $186.2M 1.18%
16 INSP INSPIRE MED SYS INC $183.0M 1.16%
17 NOW SERVICENOW INC $175.0M 1.11%
18 SAIA SAIA INC $173.5M 1.1%
19 AME AMETEK INC $173.5M 1.1%
20 HUBS HUBSPOT INC $169.7M 1.08%

Values as reported on the Q2 2023 Form 13F. Every position is in the holdings table below.

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