The Office star will play the mammal who moves into the fictional town of Quahog, Rhode Island, after a chance meeting on a fishing trip.
The 50-year-old's character is called Billy Finn, and will feature in an episode entitled Be Careful What You Fish For.
According to BBC Newsbeat, Ricky said: 'Family Guy is my favourite show at the moment.
'I watch two a night and I'm slightly obsessed. When Seth MacFarlane [creator] phoned me out of the blue and said he was a huge fan, I was delighted. It was such a joy working with the team and I really like the way my character looks too.'
Family Guy also features the voices of Seth Green and Mila Kunis.
The programme follows the Griffin family, which includes Dad Peter, a baby called Stewie and Brian the talking dog.