Last year, Mariah Yeater claimed the 18-year-old pop sensation was the father of her child following an alleged sexual encounter backstage at one of his concerts.
However, the 20-year-old woman later dropped the case after Bieber offered to take a DNA test to prove the baby was not his.
Speaking about the track, Bieber said at an album playback held in London: "It's about everything I've gone through.
"I've written a song about that whole situation with that girl who said she's having my baby - Mariah Yeater."
Bieber told an audience at the playback that he has a lot to prove with his new material, but is confident of its success.
"I definitely had something to prove but I did it justice. You'll be blown away. Every song has a piece of me. I love all of them."
Justin Bieber will release Believe in the UK on June 18 and the US on June 19.
> Justin Bieber tweets message to alleged baby mother Mariah Yeater
Listen to Justin Bieber's latest single 'Boyfriend' below: