Unisun Athletic, the Cumberland County League champions, were denied another trophy when they were beaten in a penalty shoot-out.
Mirehouse had survived a two-goal comeback and a red card to finish all square at 2-2 and then goalkeeper Alfie Maguire proved to be their match-winner.
He made two crucial saves as the West Cumbrians won the spot-kick decider 4-3 to pick up the Whitehaven Cup.
Unisun had been beaten by their main league rivals Maryport Athletic on Wednesday in the final of the Ken Glover Memorial Trophy but earlier in the season had won the Conway Cup.
So they finish the campaign with a double, instead of a possible quadruple.
Mirehouse had opened up a 2-0 lead by the break at the Falcon Complex with Callum Wilson and Nicky McAllister on target.
But then Unisun stormed back in a dominant start to the second-half and were level with goals from Jason McAleese and Shane Dorward.
The momentum was with the Carlisle side but then Mirehouse had Ryan Maguire sent-off for a second bookable offence. And somehow that seemed to inspire them. They probably had the better chances before it went to penalties.
Step forward Mirehouse keeper Alfie Maguire as his two penalty saves won his side the trophy.
