Harrington signed with the New Orleans Saints on September 19, 2008. He was the third-string quarterback behind Drew Brees and Mark Brunell for one game against the Denver Broncos. He was released only five days later on September 24, 2008, due to increasing injuries on the Saints roster. After the Saints' injury situation became more manageable, Harrington was re-signed on October 1, but was cut again on October 6. He once again re-signed with the Saints on October 12, 2008, as an inactive third-string quarterback.