A 1978 second-round draft pick of the Cowboys, Christensen was injured in the preseason and went on the IR after a successful preseason at fullback. In 1979, Dallas wanted to move him to tight end - a move Christensen did not want to make at that time. Dallas waived him, he signed with the Giants, but was waived after one game played and two weeks with the team. After clearing waivers, he was signed by the Oakland Raiders. He played mostly on special teams for the next three years, but was officially moved to tight end. In 1982, he had a break-out season and played tight end with the Raiders through the 1988 season, collecting 2 Super Bowl rings and selected to the Pro Bowl 5 times.
Following his football career Todd Christensen had tryouts with the Oakland A's and the Anaheim Angels but found his niche in Masters Track and Field where he set an age-group World Record in the Heptathlon and was the top decathlete in the world for ages 45-and-over. He also went into broadcasting, doing color commentary work for several years on NBC's NFL coverage and later college football on ESPN and the MountainWest network.
He died November 13, 2013 in the morning during surgery at a local hospital. Christensen, who has battled liver disease and other serious illnesses in recent years, was 57.