The Fall Out boy musician, 34, announced on Instagram that he was expecting his first child with his model girlfriend Meagan Camper.
"We're super excited to announce we're expecting a baby!" wrote Pete next to a photo of the couple lying down side by side. Pete is already father to five-year-old son Bronx from his previous marriage to ex-wife Ashlee Simpson.
In the sweet snapshot, Pete is pictured gently touching his girlfriend's tiny bump and sharing a kiss with Meagan. The model's white t-shirt is slightly pulled up to reveal the early signs of her pregnancy.
Pete and Meagan, who have been dating for two years, had reportedly been hoping to start a family.
"They've been planning on this for a while," an insider previously told People. "They're really excited for Bronx to have a new little buddy.
"Meagan is a big sister and has a great relationship with Bronx. She's naturally maternal so this is perfect."
The couple could be set to walk down the aisle, as just last month Pete revealed that he plans to remarry in the future.
"We talk about it a lot," said Pete. "I feel really lucky. It's, like, really interesting [to be] in a relationship with someone who is truly my best friend.
"I talk to her about everything. She will tell me when I'm being not so insane, and sometimes she's like, 'You're being a little bit insane.' It's very helpful."
The Dance, Dance guitarist divorced his ex-wife Ashlee in 2011 after three years of marriage. Ashlee, 29, recently announced her own engagement to actor Evan Ross — Diana Ross' son.
"My baby love and I are ENGAGED!!!" Ashlee told fans on Twiiter. "Hallelujah Hawaii!!"
The singer also shared a photograph of herself in her husband-to-be's arms, with her huge new engagement ring proudly on display.