On January 19, 2008, Harbaugh was appointed the third-ever head coach of the Baltimore Ravens after Jason Garrett, the team's first choice, decided to stay with the Dallas Cowboys after receiving a raise and a promotion to assistant head coach. He was not considered one of the favorites for the position because he had no head coaching experience at any level and had never been an offensive or defensive coordinator in the NFL. He impressed team owner Steve Bisciotti and Vice President of Player Personnel/General Manager Ozzie Newsome. New England Patriots head coach Bill Belichick also recommended Harbaugh to Bisciotti by phone during the interview process.
On January 23, 2008, Harbaugh hired longtime NFL offensive coach (and former head coach) Cam Cameron as offensive coordinator. (Cameron had previously hired Harbaugh as an assistant at Indiana.) Cameron was also quarterbacks coach for John's brother, Jim, during their time at Michigan. On September 7, 2008, in his debut as a head coach, John and his Ravens beat the Cincinnati Bengals.