After his much heralded contribution to the Miami Dolphins as a bruising fullback, Csonka joined the World Football League (WFL) in 1975. That league folded not long after, and Csonka became a free agent. He joined the New York Giants for their 1976 season.
Csonka started 12 games for the Giants, toting the football 160 times for 569 yards and 4 touchdowns. An injury to his knee would cut his first season short as a member of the Giants.
Being the tough dude he was on the football field, Csonka was back at it with New York for the 1977 season, running the ball 134 times for 464 yards and a touchdown.
His final campaign as a Giant saw his rushing yardage number dip to 311 yards on 91 carries, but his number of touchdowns scored jump up to 6 during the 1978 NFL season.