Rometty was voted into the post by the board of directors. As chairman, she will succeed the company's former CEO, Sam Palmisano, who is stepping down from the board.

Rometty was named as CEO last October and went on the job in January. She is IBM's ninth CEO and joined the company in 1981. She held top positions in IBM's sales and services units before being appointed to the top management job.

Rometty is already on the company's board of directors. IBM will have on the board after Palmisano steps down.