Cayton made it through to the final thanks to a victory over Staithes in the semi-final that kicked the day off, with a place against Mulgrave in the final up for grabs after Settrington conceded their place in the other semi-final.
Aussie Ben Vicary made 67 and Tom Ward 38 as Cayton posted 146, a total Staithes failed to chase down, setting up a Cayton v Mulgrave final.
Mulgrave won the toss and batted first, making their way to 137-6, Aussie Eli Sheean hitting 38 and Chris Knight 25, Jake McALeese taking 2-19.
Cayton raced out of the traps as Michael Dennis smashed three sixes and four fours in his rapid knock of 43, but they were reduced to 53-3 and then needed 10 runs to win off the final over of the contest with only one wicket in hand, Andy Raw and Craig Thompson having taken three wickets each.
The last Cayton wicket fell with nine runs still required for victory as Mulgrave sealed the silverware.
Delighted Mulgrave skipper Arron Leeman said: “This was a great advert for local cricket.
“It was a proper T20 game that had everything and went right down to the wire.
“Cayton set off absolutely flying and it looked like it would be over in 10 or 12 overs.
“The then introduction of Andy Raw and Chris Knight put the brakes on and we managed to turn it around.
“Thanks to Scarborough Cricket Club, the organisers of the competition and Beckett League officials.
“Best of luck to Cayton CC for the rest of the 2019 season.”