A Melbourne family's beloved pet cat has been thrown in to help seal the deal on a $2.2 million house sale.

Michael and Fran Perceval had failed to sell their five-bedroom Glen Iris home at auction and the property was passed in at $2,060,000, before the real estate agent negotiated a bizarre deal.

Beloved pet cat, Tiffany, has been thrown in to seal a $2.2 million house sale. Photo: 7News More

A child of one of the bidders had fallen in love with the family's four-year-old ragdoll, Tiffany, who was lounging around during an open inspection of the home - so they offered to buy the property for $2.2 million - as long as the moggy was thrown in too.

The Percevals said prospective buyers often mentioned how beautiful Tiffany was as she observed the house guests from the comfort of her couch.

The pair had jokingly suggested they would consider including the cat if the bidder offered their asking price, but they never expected anyone to actually agree.

"We didn't believe it," Fran said. "We thought 'that's ridiculous', but he honestly wanted the cat with the sale of the house."

The Perceval's agreed to include Tiffany in the contract, raising the house sale by $140,000.

They said it would be be sad to say goodbye to Tiffany, but believe she would have wanted to remain in the house.

"We've got the deal for the house and now we're leaving our beloved Tiffany," Fran said.

The couple's 19-year-old son, Sam, who owned the Tiffany, was initially unhappy about the deal, but has since come around to the idea.

"The cat will be going to a family with a younger child who will take great care of her, so Sam was fine in the end," Fran said.

The Perceval's said they plan to spend the next couple of months with Tiffany before they relocate to Ashburton in early December.