The chart-topping songstress joins Randy Jackson and fellow new judges Nicki Minaj and Keith Urban on the panel in the new series of the US singing show, following the departure of Jennifer Lopez and Steven Tyler.
She said: "I was on the fence about the whole thing. I got approached by all the shows."
Mariah went on: "He (Nick) said I should do it because it's the top, it's the cream of the crop. And I felt like, 'Do the show that's produced massive stars who have had major careers'."
Nicki confessed she surprised herself by signing up.
She referred to "a judgmental culture in hip-hop" where "sometimes you are afraid of being too famous because it's almost, like, is that even cool?"
She continued: "Being that accessible, someone you see on TV every week? I never pictured myself as that type of person. I'm still surprised that I decided to do it."