But now the person who ended up raising the little monkey is speaking out - blasting Bieber for abandoning the animal. In an interview with the U.K.'s MailOnline, Mally's keeper, Jenny Niawoehner, basically calls Bieber out.
"I would not like to meet Justin Bieber because I would not have pleasant things to say to him," says Niawoehner.
"Mally was frightened [when he arrived], he was alone, he was disoriented and we did not know how things would work out for him. He needed to be cared for constantly. I believe that Justin Bieber probably only ever interacted with him when he wanted to have his picture taken with a fan."
Animals welfare advocates say that monkeys like Mally should never be people's personal pets. Debbie Leahy, from the Humane Society of the United States, says that monkeys bred for the pet trade are typically separated from their parents at too young an age and develop behavior problems as they mature into adulthood.
"No primate species should ever be kept as a pet. They have very special needs. These are highly social animals," Leahy told National Geographic. "They need to be kept with others of their own kind; that's just critical to their psychological well-being."