The quarterback will move to Oakland in exchange for a fifth-round draft pick in 2014 and a conditional 2015 pick.
Raiders general manager Reggie McKenzie told reporters: "I've known Matt Flynn since 2007 and scouted him before and after he entered the NFL.
"Matt is a tough football player and a talented quarterback. He will get the opportunity to compete to be a starter with the Raiders. I believe Matt has that potential, but I also know he hasn't had enough experience."