The Britain's Got Talent winners appear as sad circus performers in a poster for the animal welfare charity.
Ashleigh Butler said of her involvement with the charity: "I love animals. So when I learned about the cruel ways wild animals in circuses are treated, I had to do something to help.
"Pudsey and I love to perform, but wild animals in circuses do not. Animals in the circus are whipped and beaten so that they will perform tricks. When they are not being forced to perform, they spend most of their lonely lives in tiny cages.
"No animal should be abused for the entertainment industry. Wild animals belong in the wild – not in the circus ring. And I hope that by posing in PETA's new ad I can help draw attention to this important issue."
She added: "Of course, there are a lot of fantastic circuses, like Cirque Du Soleil, which don't use animals at all."
Butler said that Pudsey enjoyed his time as a model in front of the cameras, saying: "Pudsey loved the attention and was really well-behaved throughout.
"I think he knew how important this photoshoot was to me."
Pudsey was recently revealed to have been given a £100,000 book deal with Orion Books.