AMV saw off challenges from Bartle Bogle Hegarty, WWAV Rapp Collins and Joshua to retain the £2 million creative account in a statutory review.
The agency contested the pitch with PHD and Lateral, which were awarded the media and online accounts respectively.
The decision means that the relationship between AMV and the charity will continue for at least another five years.
Farah Ramzan, AMV's deputy managing director, led the successful repitch, along with Paul Belford and Nigel Roberts, the former Ogilvy & Mather creative directors, who joined AMV earlier this year.
Ramzan said: "We're delighted by this vote of confidence from the RSPCA and welcome the opportunity to continue our track record of ground-breaking work for the charity."
New advertising will come under the control of Robbie Marsland, the RSPCA's head of campaigns, who joined in April from Action Aid.
Cilla Snowball, AMV's chief executive, denied the result of the contest was a foregone conclusion. "A statutory review is still a pitch. We went in with confidence but we knew that nothing was guaranteed, she said.
AMV has a history of producing controversial campaigns for the RSPCA, including its famous 1993 ad showing a pile of dead dogs.
Its TV commercial depicting a puppy in a holdall being tossed into a canal was one of last year's most complained about ads. However, the Independent Television Commission refused to ban it.