Amazon’s hunt for office space in Boston has led it to WeWork’s complex in Back Bay.

Amazon’s first Boston office will be located at 31 St. James Ave., part of a new WeWork coworking space that opened this month, an Amazon spokesman confirmed. The Seattle-based tech giant had sought up to 200,000 square feet in Boston for expansion, according to brokers. Amazon first leased 105,000 square feet at 101 Main St. in Cambridge’s Kendall Square in 2012 and has expanded to approximately 171,000 at that location.

The size of the Back Bay outpost was not immediately available, but the move has the potential to stabilize the office market in a neighborhood seeing an exodus of large tenants.

Houghton Mifflin Harcourt moved to Tishman Speyer’s 125 High St. and Natixis Global Asset Management relocated to Boston Properties’ new 888 Boylston tower in Back Bay, while Partners Healthcare consolidated at a new headquarters in Somerville. Wells Fargo also is moving to 150,000 square feet at 125 High St. and relocating nearly 800 employees from 1 Boston Place, 101 Federal St. and 200 Berkeley St.

The moves open up 800,000 square feet of office space in the 13.2-million-square-foot Back Bay office submarket. The availability rate at year’s end was 18.4 percent, according to research from Cresa Boston, with average Class A rents of $62.08 per square foot.