The actress joins several others in Bollywood who have supported the animal rights charity.
Mirza told Mumbai Mirror: "Skinning animals alive or beating them to death for a pair of boots or a purse cannot be justified.
"By choosing widely available fake snake and mock croc, you can pay tribute to these animals' beauty without stealing their skins and killing them."
The campaign features Mirza appearing as though she has been skinned alive like a snake.
Joaquin Phoenix also narrates an undercover video for the site which shows viewers how animals are harmed by the snakeskin industry.
Last year, actor Sonu Sood posed shirtless for the controversial charity in an advert with the tagline: "Strong Body. Tender Heart. Go Vegetarian."
He was beaten by Bollywood rival Shahid Kapoor in the vote for 'Sexiest Vegetarian of the Year'.