After the 2005 season, Detroit signed free agents Jon Kitna and Josh McCown, and traded Harrington to the Miami Dolphins on May 12, 2006, for a fifth-round draft pick in 2007, after meeting performance stipulations in Miami (the pick was later traded to the New Orleans Saints). Harrington started the 2006 season as a backup behind new Dolphins quarterback Daunte Culpepper. During his tenure with the Lions, Harrington started 55 games and had a record of 18 wins and 37 losses.