Seaport's $879-a-foot sale marks a narrow trophy comp

Clarion Partners has sold One Marina Park Drive, a 494,938-square-foot office tower in Boston’s Seaport District, to Oxford Properties for $435 million, according to IREI. The deal is the largest pure-play office sale in Boston in five years and one of 2026’s most impactful office transactions. At $879 per square foot, the price can be read as a Seaport outlier or a market-wide recovery; the building’s particulars argue for something narrower.

The 18-story tower arrived in 2010 as the anchor commercial asset of The Fallon Company’s $4 billion Fan Pier development and enters Oxford’s portfolio 99 percent leased to a high-credit roster, with LEED Gold and WiredScore Platinum certifications, 375 below-grade parking spaces, and harbor views through floor-to-ceiling glass. Behind it sits a submarket that has produced 22 percent Tier 1 rent growth since 2019, and the site itself is one of Boston’s last direct waterfront parcels in Fan Pier, immediately adjacent to Vertex Pharmaceuticals’ 1.1-million-square-foot global headquarters.

The surrounding Fan Pier area supplies the amenity set underwriters now expect from a core address: more than 35 dining options within two blocks, 1,200 luxury housing units, 50 retail stores, plus hotels and museums. South Station’s Red Line, commuter rail, and the MBTA ferry at Rowes Wharf sit a short walk away. IREI describes the barriers to entry as insurmountable, and for the Seaport that phrase is close to literal.

All of that makes the sale a trophy-office clearing price rather than a broad-market data point. As this publication has argued, office has moved from mark-to-market to trade-to-trade, with clearing prices on the commodity side set by local, vacancy-tolerant buyers. This deal does not disturb that view; it sharpens the divide. A 99-percent-leased, WiredScore-certified, waterfront tower is essentially a long-duration bond with a view, and the buyer that steps forward for it is not the same buyer that will step forward for a 60-percent-leased 1990s building.

IREI frames the transaction as a return of institutional capital to the Boston office market, and that is true in a precise sense: the capital is returning to the Seaport, where Tier 1 rents have grown 22 percent since 2019 and modern, amenitized product is scarce. It is not yet returning to the parts of Boston that need repositioning.

Part of why this is the largest pure-play office trade in five years is that the market has been stalled: sellers held trophy assets to avoid realizing losses on older office, and buyers waited for prices to reset. The Seaport sale offers a mark that both sides can point to.

A market that goes half a decade without a clean, large office trade leaves owners and lenders without a benchmark to underwrite against, and that absence is the real significance of the five-year no-trade streak, not this sale alone. The Seaport deal fills that gap for a narrow tier of assets; the price it establishes will become the reference point in appraisals and lender valuations for other fully leased, modern towers in Boston. It will not become the reference point for the buildings that most need capital to lease up and reposition.

For Oxford, the underwrite is a core-office bet with no vacancy to harvest. With the building already essentially full, the leasing upside is compressed, so the return rests on contractual rent growth, the quality of tenant credit, and the Seaport’s continued upward trajectory. The asset’s modern specifications and certifications argue it will not suffer the functional obsolescence that has already hit office towers from the 1980s and 1990s. For Clarion, the exit converts a long hold at a moment when the submarket has delivered two decades of appreciation, and it hands Boston its first clean comp for a large, fully leased tower.

The danger is that a headline trade like this becomes shorthand for “office is back.” The evidence supports something narrower: one asset, one submarket, one price. Buildings without the Seaport’s water, transit, and amenity package are unlikely to command anything near this mark, and their clearing prices are still being established in transactions that never make the same headlines. The Seaport sale sets a comp for the Seaport. The next test is the first large Boston office trade outside it, and the spread that price reveals between the two markets. For now, that spread is roughly $879 a foot on the happy side; the other side is still being marked.