Ben "Dr" Lupo, who reportedly signed a multi-million dollar exclusivity deal with Twitch in 2019, will now stream exclusively on YouTube.
The American, 34, known for playing Fortnite, Destiny, Escape from Tarkov and Among Us, has the 26th most followers on Twitch, at 4.5 million.
Twitch said it wished him "nothing but the best in everything that comes next".
He made the announcement in a glossy promotional video complete with computer graphics and welling orchestral music.
Like many popular Twitch streamers, Dr Lupo already uploads archives of live broadcasts and highlight reels to YouTube, where he has 1.75 million subscribers.
But changing platforms, or even games, can lead to a large loss of followers.
In 2019, Tyler "Ninja" Blevins signed an exclusive deal reportedly worth millions of dollars with Microsoft's streaming service Mixer.