Dick Costolo Steps Down as CEO of Twitter, Jack Dorsey to Serve as Interim CEO

The Twitter logo is shown on smartphone. Dado Ruvic/Reuters

On Thursday, Twitter announced Dick Costolo will step down as CEO, effective July 1. Jack Dorsey, the co-founder of Twitter, will serve as interim CEO while the board of the company searches for someone to fill Costolo's role.

"I am tremendously proud of the Twitter team and all that the team has accomplished together during my six years with the Company. We have great leaders who work well together and a clear strategy that informs our objectives and priorities. There is no one better than Jack Dorsey to lead Twitter during this transition. He has a profound understanding of the product and Twitter's mission in the world as well as a great relationship with Twitter's leadership team," Costolo said in a statement. "I am deeply appreciative of the confidence the Board, the management team and the employees have placed in me over the years, and I look forward to supporting Twitter however I can going forward."

"The future belongs to Twitter thanks in large part to Dick Costolo's dedication and vision. Dick has put a world-class team in place and created a great foundation from which Twitter can continue to change the world and grow," Dorsey said. "We have an exciting lineup of products and initiatives coming to market, and I look forward to continuing to execute our strategy while helping facilitate a smooth transition as the Board conducts its search."

It is unclear why exactly Costolo stepped down, however, Twitter has struggled to expand its service, much to the frustration of investors.