"She probably would have been [a Belieber]," the rapper told Vulture at the premiere of the new movie Pain & Gain on Tuesday night.
He was referring, of course, to Bieber's note, in which the 19-year-old pop star wrote, "Truly inspiring to be able to come here. Anne was a great girl. Hopefully she would have been a belieber."
But 50 Cent's support went even further. He added that Bieber has the potential to reach the same heights, career-wise, as the late Michael Jackson.
"He can be one of those guys who can eventually transition like that," he said.
Meanwhile, Pain & Gain star Mark Wahlberg simply had some words of advice for Bieber.
"I think it's best to put down the phone and Twitter and all that stuff, and just be a little more low-key right now," the actor remarked. "Because they're watching every move he makes, everything he says, and less is more. Go take a vacation."