The Victoria's Secret model, who recently gave birth to her second child Noah Phoenix, was recently photographed carrying a puppy that had been dyed pink and purple.
PETA has now released a statement to E! News complaining about Ambrosio's actions.
"What most people don't know is that dyeing a companion animal's fur can cause the animal stress and can lead to complications or allergic reactions that endanger the animal's health," the organisation said.
"Our dogs and cats love us regardless of how we look - why not extend the same kindness to them?"
PETA previously criticised Jersey Shore stars Snooki and JWoww for dyeing dogs' fur, while other celebrities recently slammed by the organisation include Kim Kardashian and Mary-Kate and Ashley Olsen.