Westfield Q1 2026: Growth With an AI-Infrastructure Tilt

Westfield Capital Management, a Boston growth manager, reported a $23.83B U.S. equity book for the quarter ended March 31, 2026 (Form 13F-HR, accession 0001177719-26-000018, filed 2026-05-11). The book sat nearly flat in value, and its composition tells a clear story: this is a growth portfolio that pairs megacap technology with the physical infrastructure of the AI build-out.

At the top, Nvidia (NVDA) and biotech Ascendis Pharma (ASND) are tied as the largest positions at 4.62% each. But what distinguishes Westfield from a pure megacap book is what comes next: Comfort Systems USA (FIX), a mechanical contractor that builds data-center cooling and power systems, and Vertiv (VRT), a leading maker of data-center power and thermal equipment. These are the picks-and-shovels of AI infrastructure.

The quarter was light on big moves — a 6% add to Nvidia, modest trims to Comfort Systems, Vertiv, and Alphabet — consistent with a growth manager fine-tuning rather than overhauling.

Growth plus AI infrastructure

After Nvidia and Ascendis come Comfort Systems at 3.59%, Apple (AAPL) at 3.34%, and an international holding at 2.93%. The book continues with Microsoft (MSFT), Alphabet's GOOGL shares, aerospace supplier Howmet Aerospace (HWM), Vertiv, and Amazon (AMZN).

The pairing is the point. Alongside the familiar megacaps, Westfield owns the companies that physically enable AI compute — data-center construction (Comfort Systems), power and cooling hardware (Vertiv), and aerospace components (Howmet). With 250 positions and the ten largest at roughly 30% of the book, it is a diversified growth portfolio with a distinct infrastructure thread.

A quarter of fine-tuning

Westfield made no dramatic moves. It added 6% to Nvidia and 21% to its international position, while trimming Comfort Systems (-7%), Vertiv (-16%), Alphabet (-7%), and Ascendis (-7%). Most other top holdings, including Apple, Microsoft, and Amazon, were held roughly flat.

Trimming some of the AI-infrastructure names after their strong runs while adding modestly to Nvidia suggests a manager taking some profits in the more volatile build-out plays while keeping its anchor in the chip leader. The reported value has held in a tight $20B-$24B band, reflecting steady positioning.

What it means for 13F readers

Westfield is a useful example of how a growth manager expresses the AI theme beyond the obvious chip names — reaching into the construction, power, and cooling companies that the data-center boom requires. The interplay between its Nvidia anchor and its infrastructure holdings is the thread to watch. Track the firm's quarter-over-quarter holdings on the Westfield Capital filer page.

FAQ

What is Westfield Capital Management?

Westfield Capital is a Boston-based growth equity manager. It reported a $23.83B U.S. equity 13F book for the quarter ended March 31, 2026, across about 250 positions.

What are Westfield's largest holdings in Q1 2026?

Nvidia and Ascendis Pharma are tied as the largest at 4.62% each, followed by Comfort Systems USA (3.59%), Apple (3.34%), and an international position (2.93%).

How does Westfield play the AI theme?

Beyond megacap chips like Nvidia, Westfield owns the physical infrastructure of AI — data-center contractor Comfort Systems, power-and-cooling maker Vertiv, and aerospace supplier Howmet.

What did Westfield do in Q1 2026?

The firm fine-tuned rather than overhauled — adding 6% to Nvidia and trimming Comfort Systems (-7%), Vertiv (-16%), and Alphabet (-7%), while holding most other top positions roughly flat.