On Wednesday, Baby crooner Bieber, 20, posted a picture on Instagram with Mahone, 17. He simply captioned the photo, "New music."
"Justin knew Austin had been in the studio working on his album," a source tells PEOPLE. "And he had a song he thought could be really perfect to do with Austin."
You might think the two would be competitors, but it seems Bieber gets on famously with Mahone, whose current single Mmm Yeah featuring Pitbull has been consistently climbing the charts and dominating the radio.
"Austin and Justin have met before and they really respect each other's music," the source continued. "They work with a lot of the same producers, so they got together in the studio."
Mahone – whose die hard fans call themselves "mahomies" – will release his highly anticipated album later this year. And he's not being shy about how he thinks fans will receive the new collaboration.
"What an amazing song last night," he wrote with his own Instagram of Bieber's photo. "The world isn't ready!"