Colchester guaranteed another season in League One as goals from Gavin Massey and Tom Eastman saw off Carlisle.
The Essex club needed a win to guarantee their survival in the third tier and their nerves were finally settled when Massey struck.
Massey reacted quickest to head into the net after Billy Clifford's effort rebounded off the crossbar.
Eastman wrapped up the three points as he headed in David Wright's looping ball from the by-line.
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Colchester United manager Joe Dunne told BBC Essex:
"Mission accomplished. We talked about getting the job done ourselves, and I thought we were magnificent.
"We had a gameplan that worked spot-on. We frustrated Carlisle, killed the game a bit, made sure we were counter-attacking.
"I thought we controlled the first half and the game developed into exactly what we wanted it to. It doesn't matter what the other team did - we've done it."