Mr Mayer will be joining ByteDance on 1 June.
Alex Zhu, the current President of TikTok, will transition to ByteDance VP of product and strategy, which the company said are his areas of passion. He was also seen as a potential successor to Disney CEO Bob Iger; instead, Disney Parks, Experiences and Products Chairman Bob Chapek was named CEO in a sudden announcement in February.
The unexpected move, announced this afternoon, comes a few months after Mayer was passed over for the top job at Disney following longtime Disney CEO Bob Iger's decision to step down from the helm of the company.
TikTok, meanwhile, has hired a number of US executives and employees to run its business and review content on its app. Vanessa Pappas, a former YouTube executive who joined TikTok as one of its American chiefs previous year, said in a November blog post that the company's United States-based team would call the shots on TikTok's USA business, including by setting specific rules for American users.
The executive was credited with helping to develop and launch Disney Plus, which has been a consumer if not yet profit success story with 54 million paid subscribers as of earlier this month, according to Disney.
Yiming, the ByteDance chief executive, said he thought Mayer could "take ByteDance's portfolio of products to the next level".
More immediately, Mayer could also have his work cut out on the political front. TikTok faces bipartisan questions on Capitol Hill over privacy and surveillance concerns.
From 2007 to 2010, Ms. Campbell served as President and General Manager of WABC-TV - New York, the group's flagship station in the nation's largest television market, where she was responsible for WABC-TV and all of its ancillary businesses, including two additional digital platforms and "Live with Regis and Kelly". For example, branches of the USA military have banned their members from having the TikTok app on government issued phones.
"With over 110 million downloads in the USA alone, TikTok is a potential counterintelligence threat we can not ignore", the lawmakers wrote. Josh Hawley (R-Mo.), who noted his frustration with TikTok's refusal to send high-level executives to Washington to testify before Congress.
"[TikTok] previously told me they couldn't attend hearings and testify because executives were located in #China", Hawley tweeted. "But this new executive lives in the USA". I look forward to hearing from him.
"This is a huge coup for for TikTok and a huge loss for Disney", Greenfield said.
He did not respond to a request for an interview.
Zhu a year ago had sought to meet with leaders to allay their worries, though the company's executives declined to appear at a congressional hearing in March to answer questions about their practices. In late April, TikTok topped 2 billion global downloads; in Q1, it had the best quarter of any app ever, per Sensor Tower.
"I'm thrilled to have the opportunity to join the wonderful team at ByteDance", said Mayer, "On a personal note, I'm thankful to the entire Disney team for the tremendous accomplishments we achieved together".