The Jism 2 star is seen posing alongside rescued dog Kaali, with the caption: "Birth Control! Dogs Need it Too. Sterilise Your Dogs and Cats."
In an interview with PETA India, Leone said: "I believe that every single dog should be spayed and neutered. You don't want to continue the cycle of homeless dogs or cats.
"And spaying and neutering also keeps them healthy. It prevents them from having different diseases that they can get if they are not."
Leone, who was named the 2003 Penthouse Pet of the Year and made her Bollywood debut last year, appeared in an earlier ad for PETA with the caption: "Too much sex can be a bad thing."
The makers of Jism 2 donated the film's wardrobe, including lingerie worn by Leone, to PETA India for auction.
The former porn star, who shares her home in Los Angeles with two rescued dogs, has confirmed that she will star in the sequel to the horror-thriller Ragini MMS.