Second-half goals from Stuart Shaw and Leigh Dunn handed the Wearside League outfit a 2-0 victory against a Blues’ youth side.
The victory was celebrated by a vocal travelling support from Cleator Moor at Brunton Park.
Their manager Dene White said: “I’m absolutely delighted.
“We were playing against some full-time lads, who were clearly fitter than us - but we didn’t stop from minute one to 90.”
The visitors started well and went close through Dunn, Callum Birdsall and Shaw.
Carlisle’s Jack Egan was then denied by Moor keeper Connor McAleavey when clean through.
The visitors were furious at being denied a penalty shortly before half-time when Joe Breen appeared to impede Dunn in front of goal.
Ryan Hall then missed a great chance for Cleator Moor after rounding keeper Morgan Bacon.
But the deadlock was then broken on the hour mark as Shaw headed a right-wing cross from sub Darren Little past Bacon.
Cameron Salkeld, who played 90 minutes for the reserves at Burnley in the afternoon, came on for the last 12 minutes as United looked for a way back.
But Carlisle were killed off six minutes from time, when a weak backpass saw Little tackle keeper Bacon, who then brought the substitute down.
Little’s penalty hit the post, but Dunn fired home the rebound.
United academy manager Darren Edmondson said: “Cleator Moor did the right things and overall deserved to win.
“There were still positives to take – at half-time we thought we should have been ahead, and some of our passing and movement was good.
“But we just missed a couple of our better attacking players, who could have helped us going forward.”
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