Mulgrave skipper Nick Gibson won the toss and stuck Flixton into bat first, a decision that looked to have paid off as their young batting line up could only muster a total of 89-6 from their 20 overs.
Finlay Ward top-scored for Flixton with 28 not out from 45 deliveries, hitting one six and a four, while Charlie Colley was the only batsmen in their side to make double figures as he contributed 20.
Crucially, Mulgrave conceded 22 extras that allowed Flixton to make it up to 89-6.
Peter Stentiford bagged 2-8 from four overs, while Ben Duell (1-8), Aidan Duell (1-15) and Dominic Ingham (1-28) all contributed with the ball for Mulgrave.
Despite only chasing a modest total, Mulgrave collapsed to 70-9 from their 20 overs in reply in the face of superb bowling from Colley (3-9), Finlay Ward (2-6), Callum Hatton (2-10) and Alex Potter (2-12).
Only four Mulgrave batsmen managed to make it to double figures, with Stentiford top-scoring on 15.