The 54-year-old music producer and record executive is said to be joining the judging panel on the US version of the X Factor - and leaving Def Jam frees up his time to join Simon Cowell's show.
In his leaving letter obtained by JustJared.com, he reportedly wrote: 'To my Island Def Jam family: After much consideration, I have decided to leave my position as Chairman of the Island Def Jam Music Group.
'I have always thrived on growth and the next great challenge, and I look forward with much enthusiasm to what the future holds.
'I am extremely proud of our beautiful roster and all we have accomplished in my seven years with IDJ. We continue to have incredible success together with today’s most phenomenal superstars - Rihanna, Justin Bieber, Mariah Carey (she reportedly will follow L.A.), Kanye West, Bon Jovi, Jennifer Lopez, Ne-Yo, Rick Ross, The Killers, The-Dream, Chrisette Michele, Jeezy and Ludacris to name a few.
'I want to thank all of you for your amazing contributions.'