The "Baby" hitmaker took to his Instagram page on Saturday, December 22, to introduce fans to the couple's new ball of fur, posting a topless picture of himself in bed with the tiny dog sitting on his shoulder.
"Meet our dogson his name is #Oscar," the pop superstar wrote, under which Hailey commented, "My babies".
Justin also wished followers well for the holidays as he showed off an image of Oscar's new bed and food corner on his Instagram Story timeline.
"Merry Christmas from Oscar," he captioned the shot.
He followed it up with a series of videos of Oscar crawling over his tattooed chest and others of Hailey beaming with delight as she cuddled and kissed the new addition to their family.
However, while his wife was clearly delighted with the early Christmas gift, Justin admitted he wasn't showing as much enthusiasm because he wasn't feeling well.
"I'm sick," he wrote across one clip. "That's why I'm frowning".
Meanwhile, Hailey can't stop expressing her joy over the animal, which is thought to be a Maltese Yorkie, according to TMZ.
She also shared multiple photos and videos of the pup on her Instagram profile, gushing alongside one, "My Christmas baby. Oscar Bieber."
The holidays are the couple's first as husband and wife, after exchanging vows in a courthouse ceremony in September, just weeks after Justin, 24, proposed over the summer.
And it seems the puppy will help the newlyweds prepare for their future as parents - if Hailey's recent interview with Vogue Arabia is anything to go by.
"I love kids and I can't wait to have my own. I would say now that's a closer reality," the 22-year-old teased, seemingly referencing her marriage to Justin.