The 61-year-old has hosted a range of popular programmes on Rai and had been the presenter and artistic director of the iconic Sanremo Music Festival, which is also screened by the network, for the last five years.
He becomes the latest in a string of top TV stars to leave the broadcaster over the last few years.
Last summer, journalist Bianca Berlinguer, the daughter of late Italian Communist Party leader Enrico Berlinguer, who presented the Cartabianca political talk show on the Rai3 channel, quit Rai after 34 years before joining Mediaset.
Rai3 also recently lost two other popular left-leaning chat show hosts, Fabio Fazio and Lucia Annunziata, a former Rai chair.
Fazio, whose show was not renewed and moved to the Warner Bros Discovery Nove channel, said he was a victim of an alleged purge by the government.
Former Rai president and veteran journalist Annunziata also quit complaining about government meddling.
Amadeus is tipped to move to Nove too.
ANSA
