NEW YORK CITY—Annaly Capital Management Inc. said Monday afternoon its president, Kevin Keyes, would also take on the role of CEO, effective Sept. 30. Wellington Denahan, who cofounded Annaly in 1997, is stepping down as CEO, although she will remain chairman of the board and also serve as executive chairman, focusing on strategic and capital allocation decisions.

“I'm very proud to have co-founded a company that has grown to become the largest mortgage REIT in the world while delivering competitive returns through a wide range of market conditions,” Denahan says. “I look forward to continuing to work with Kevin and the team as we navigate the opportunities ahead.”

Denahan assumed the role of CEO in 2012 following the death of longtime head Michael Farrell, with whom she cofounded Annaly. Under her leadership, the REIT has expanded its focus from residential MBS to commercial real estate debt.

Keyes joined Annaly in 2009, after advising it while with Merrill Lynch & Co. “I know the opportunity that lies ahead for Annaly is enormous and I am honored and energized to lead along with Wellington going forward,” he says. “We have further developed and expanded the Annaly investment teams over the past few years and are now more prepared than ever to capitalize on our targeted options for growth in the industry today.”