Cambridge made a victorious return to the Football League after a nine-year absence as Richard Money's men beat Plymouth 1-0.
The U's, who last played in League Two in May 2005, scored the only goal in the 61st minute when Josh Coulson powered home from close range after Ryan Donaldson's corner was flicked goalwards by Kwesi Appiah.
They had already spurned a major chance in the 11th minute when Carl McHugh controlled Appiah's cross with his arm, only for Adam Cunnington's penalty to be comfortably saved by Plymouth goalkeeper Luke McCormick.
Coulson's defensive partner Tom Bonner had headed over in the first half, and Appiah curled wide, while Reuben Reid was central to Plymouth's scoring chances. He forced Chris Dunn to push the ball away with a powerful drive on the stroke of half time, and brought a fine save from the Cambridge stopper 15 minutes from time.
Greg Taylor could have made the game safe 11 minutes from the end when he surged through and fired wide but Coulson's goal proved enough.