Although it was thought that the music producer - who has been on the panel of the show since it began - would take on the role of a ''mentor'' behind the scenes for the upcoming season, he has agreed a deal with Fox to stay on as a judge after negotiations with Enrique Iglesias fell though, according to Deadline.
Appearing to confirm the news, his former co-star Simon Cowell tweeted: ''Just heard Randy is back on Idol. Right decision.''
Mariah is not thought to be a fan of Nicki's, although producers are delighted at the prospect of conflict between them both.
Instead the 'Fantasy' hitmaker is said to be keen for Lenny Kravitz to sign up to the show.
A source said recently: ''Mariah would love to have her dear friend Lenny Kravitz sit next to her on the 'American Idol' judge panel. She thinks he would be the perfect choice because he is extremely talented and knows music inside and out.''