In his latest album Believe, Justin’s song 'Maria' is a message to the extreme Belieber who demanded a DNA test and some serious child support for the kid she says he fathered.
"I just wanted the world to know that it wasn't true, that was all I was really focused on," Justin told The Independent.
"I feel sorry for her in a way. Whatever she's doing, she's obviously not in the right state of mind, to be doing all that, be saying such mean things."
Mariah dropped the paternity suit in January this year, but the experience inspired Justin to write a song about it, which he compares to the Michael Jackson tune 'Billie Jean'.
"'Billie Jean' was the record I was kind of chasing with this song," Justin said. "The opening [of 'Maria'] is, 'She said she met me on the tour, she keeps knocking on my door, she won't leave me. Leave me alone.' So it's pretty good. The words are really powerful in the song."
Whereas 'Billie Jean' was fictitious, Justin believed the reality of his own situation would set the song apart.
"With the 'Billie Jean' story it was so mysterious. With this, it's so powerful because it actually happened, and people know the story and what actually happened," he said.
"So the fact that it's gonna be in the song and people can hear it, I think that's gonna put two and two together and that'll make them like it more."
Justin's mentor Usher was in two minds about the song, believing it would give Mariah more publicity than she deserved.
"I didn't think it was foolish, but I didn't understand why he was giving her so much accolade," he said.
"But I thought it would be genius. This is what people would want to hear here is a crazy occurrence that did happen, and you never really chose to speak about it in the press, and here you have an opportunity to be inspired by it.
"Can't be a bad thing. Us artists are always searching for inspirations."