Linda Yaccarino, the president of NBCUniversal’s advertising department, resigned amid rumors that she had been chosen to manage Twitter.
After working for the media company for 12 years, Ms. Yaccarino announced her departure from NBCUniversal with “immediate effect.”
It came after allegations that she was in negotiations with billionaire Elon Musk to lead Twitter.
In a post on Thursday, Mr. Musk announced that “she” will begin working for him in six weeks.
In his message on the site, he did not identify the new CEO, and the business has not yet announced the change.
The businessman, who paid $44 billion for the social media network last year, has been under pressure to find a new CEO and shift his attention to other projects.
Mr. Musk declared he would continue to play a role at Twitter as executive chairman and CTO.
Ms. Yaccarino would bring substantial experience to Twitter in the area of advertising, where Mr. Musk’s acquisition of Twitter has generated controversy.
Mr. Musk sacked thousands of employees right once, including those who were in charge of handling offensive posts.
He also changed how the service authenticates accounts, charging for blue ticks in a move that some criticized for making it easier for false information to proliferate.
Many big companies halted their spending on the platform in the weeks after he took charge, concerned about how their brands might be affected by changes he was making.
That was a big blow to Twitter, which has historically depended on advertising to make money.
Mr Musk told the BBC last month that many of those companies were returning.
But the site under his leadership continues to face mistrust, Ms Yaccarino reminded Mr Musk at an advertising conference last month.
“The people in this room are your accelerated path to profitability,” she said. “But there’s a decent bit of sceptics in the room.
“There’s people who cannot separate, they’re challenged by separating the man, his opinions and the microphone he now owns.”