He has been named the chief executive officer of TikTok and chief operating officer of ByteDance, the platform's Chinese parent company.
TikTok, an app where users post short videos, has seen an explosion of growth since its US launch.
But that increased popularity has led to scrutiny by the US government over its ties to China.
Mr Mayer will be responsible for ByteDance's "global development" including emerging business, gaming and music.
"I'm excited to help lead the next phase of ByteDance's journey as the company continues to expand its breadth of products across every region of the world," Mr Mayer said in the release.
He will be the first CEO of TikTok.