The 41-year-old actor initially refused the part of South Africa's first black president in 'Mandela: Long Walk To Freedom' and hung up on his agent when he was offered the part.
He was worried that would couldn't bring enough credibility to the role and suggested Morgan Freeman - who played Mandela in the 2009 film 'Invictus' - for the role instead.
Speaking in the January issue of Reader's Digest magazine, he said: ''You know, I was really, really sensitive [about the role]. My agent called up to ask if I wanted to play Mandela and I put the phone down on him. I was like, no way. Mandela? Couldn't do it.
''You're asking me to play Mandela, do you think I'm going to play a f***ing Disney Mandela? Don't ask me to do that yeah?
''Then I thought to myself, called him back and said, 'Can I be honest? If it's a grey-haired version of the fist-pumping Mandela, I'm not the actor to bring in. I'm not Morgan, go with Morgan.''
Idris' portrayal of a young Mandela during his struggle against apartheid rule in South Africa has already generated rumours of a Best Actor Oscar nomination.
The actor and musician has also dedicated his new album to the former South African President - who died aged 95 last Thursday (05.12.13), claiming it is a ''love letter'' to the late leader.
He told the Daily Star newspaper: ''The album will be called 'Mi Mandela'. I went back to South Africa and worked with some great musicians. I'm really proud of the album. I'll wait until the film has died down so it doesn't get muddled but I'll release it in the New Year.
''Basically, it's a love letter from me to Mandela about me playing him.''