The investors criticized the company over its share price, conflicts with its external adviser and management decisions. The ouster of its chief executive, Nicholas Schorsch, who sat on the boards of the REIT and the advisory firm, propelled activists further. They requested big changes and, ultimately, a sale.

Image Worldwide Plaza at 825 Eighth Avenue, a coveted office property, is owned by New York REIT. Credit... G. Paul Burnett/The New York Times

Under pressure, New York REIT sold off four noncore properties for $75.7 million to focus solely on higher-quality properties in Manhattan, and added two independent board members. It also resumed a search for a buyer, which it had started in October 2014, months after going public, and had abandoned in May 2015.

Its stock price surged on the takeover chatter, and by December, there was talk of a possible deal to sell. The shares rose to a high of $11.90 in December, from a low of $8.87 in May. Two weeks ago, New York REIT announced a plan to merge with JBG Companies, based outside Washington, but New York REIT’s stock has fallen back to $9 a share again.

Mr. Cohen, who bought into New York REIT in mid-2015 when its stock price was at about $9, sold his stake in October and November at more than $11 a share and collected dividends as well, netting about a 25 percent return for his six-month investment. “I thought it was close enough to fair value,” he said. “And we didn’t want to hold it because of the risk that a transaction wasn’t consummated.”

New York REIT declined to comment.

In the past, many activists have avoided the REIT sector because of its smaller size. REITs also have a reputation for being ruled by chief executives more concerned about building empires than stock prices, and reluctant to sell their companies.

But analysts expect that turbulence from activist investors will continue this year. At least seven new campaigns began in the first four months of 2016.

“REIT activism will become more frequent and more mainstream” in 2016, Adam Emmerich, a partner at Wachtell, Lipton, Rosen & Katz, said in an interview last month.