Boston Partners Q1 2026 13F: Deep Value, Maximum Spread

Boston Partners filed a 13F equity book of $95.47 billion for the quarter ended March 31, 2026, essentially flat from the prior quarter (down 1.2% on a holdings basis, Form 13F-HR filed 2026-05-11, accession 0001386060-26-000017). The headline number is unremarkable. The portfolio's shape is the story.

This is one of the most diversified institutional books in the 13F universe. Boston Partners' single largest position — JPMorgan — is just 2.18% of assets. The ten largest holdings combined account for only 13.61% of the portfolio; the other 86.39% is spread across hundreds of names. For a value manager running roughly $95 billion, that is a deliberate philosophy: own the cheap names broadly, let no single bet dominate, and harvest the mean reversion across the whole book.

Against that backdrop, the quarter's most revealing move was an exception to the rule — a high-conviction $1.41 billion brand-new position in Cencora (COR), which vaulted straight to the third-largest holding. When a manager that almost never lets a position exceed 1.5% opens a new name at that size, it is worth paying attention.

A top ten that reads like a value screen

The largest positions span financials, healthcare distribution, energy and gold — the classic hunting grounds of deep value. JPMorgan leads at $2.08 billion, followed by US Foods ($1.51B) and the new Cencora stake ($1.41B). Energy is well represented through Marathon Petroleum ($1.38B) and Diamondback Energy ($1.14B), and Kinross Gold ($1.11B) adds a precious-metals hedge.

The mix tilts firmly toward cash-generative, reasonably-valued businesses rather than growth. The one megacap-growth name in the top ten, Amazon at $1.14 billion, was added to (+10% shares) — but even it sits below 1.2% of the book. LPL Financial was the most aggressively increased top-ten name at +16% shares.

Diversification as the defining feature

The concentration chart makes the philosophy unmistakable. Where a high-conviction manager might run 40-50% of assets in its top ten, Boston Partners keeps that figure under 14%.

That structure has consequences worth understanding. It dampens single-stock risk and makes the book behave more like a diversified value factor than a stock-picker's portfolio — but it also means individual position changes rarely move the needle, which is precisely why the outsized Cencora add stands out. The firm also showed it will cut decisively when the thesis breaks: it slashed Novo Nordisk by 97% and UnitedHealth by 88% of shares, and exited 86 positions outright.

AUM history: steady through the cycle

Boston Partners' 13F book has climbed gradually from about $80 billion in mid-2024 to the mid-$90 billion range, peaking near $97.4 billion in Q3 2025 before settling at $95.47 billion.

Unlike growth-heavy peers whose AUM swung violently with the tech tape, Boston Partners' diversified value book has tracked a far smoother path — the eight-quarter range is roughly $80B to $97B with no double-digit quarterly drawdown. That stability is the structural payoff of refusing to concentrate.

What the quarter signals

Two threads run through the filing. First, conviction where it counts: the $1.41 billion Cencora purchase and continued energy exposure (Marathon, Diamondback) point to a manager finding value in healthcare distribution and cash-rich energy. Second, discipline on the way out: the deep cuts to Novo Nordisk and UnitedHealth show the firm rotating out of pharma and managed-care names where the value case eroded.

For investors, Boston Partners is a useful read on where systematic deep value sees opportunity — not in any one heroic bet, but in the breadth of cheap names it is willing to own. Track the next filing to see whether the Cencora conviction holds. Explore the complete book on Boston Partners' full 13F portfolio.

FAQ

How large is Boston Partners' 13F portfolio in Q1 2026?

Boston Partners reported a 13F equity portfolio of $95.47 billion for the quarter ended March 31, 2026, essentially flat (down 1.2% on a holdings basis) from the prior quarter.

What is Boston Partners' largest holding?

JPMorgan is the largest position at $2.08 billion, or 2.18% of the book. Boston Partners runs an unusually diversified portfolio in which no single name exceeds about 2.2% of assets.

What did Boston Partners buy in Q1 2026?

The standout was a new $1.41 billion position in Cencora (COR), now the third-largest holding. The firm also added to Amazon (+10% shares) and LPL Financial (+16% shares).

How concentrated is Boston Partners' portfolio?

Very lightly. The ten largest positions total just 13.61% of assets, with the remaining 86.39% spread across hundreds of value names — a deliberately diversified, factor-like structure.