Merrion will represent Leinster in the All-Ireland T20 Cup next month as they beat YMCA by six runs in a pulsating contest at sun-drenched Sydney Parade.
Jack Carty was the Merrion hero in a Man-of-the-Match display as he scored a half-century and conceded just nine runs from two crucial overs, the 18th and the 20th.
Batting first, the Anglesea Road side lost Michael Lewis in the fifth over, but Carty in company with the ever consistent John Anderson (28) steadied the nerves as they added 63 in seven overs.
Irish passport holding Australian Carty also shared a partnership of 75 in 11 overs with former Irish international Dom Joyce, who struck six fours in a fluent 43 from 34 balls.
Carty top scored with 59 from 50 balls (7 fours, 1 six) as Merrion finished on 150 for 7 - two wickets in the last over for Tom Anders (2-30), while James Forbes (2-18) also picked up a brace.
Rory Anders got the YMCA chase off to a flying start by depositing Hugh Kennedy over the ropes twice in the opening over, but was run out from the first ball of the second to put a dent in their hopes.
Skipper Jack Tector departed cheaply, but younger sibling Tim made a run-a-ball 41, putting on 58 in nine overs with Curtis Campher (31).
As the rate climbed though the chase became more frenzied, with two further run outs as the nerves increased.
Bobby Gamble (24), Mitchell Thompson (15) and Tom Anders all reached double figures, but the rate kept climbing.
A word for spinner Amish Sidhu, whose conceded only 15 runs in his four overs spell to increase that scoreboard pressure.
26 were needed from the last two overs, but 14 from the penultimate one reduced that equation to 12 from the last.
It was to be Carty's and Merrion's day though as he held his nerve to deliver the cup, with Anders unable to clear the ropes from the final ball, which would have meant a Super Over.
Merrion join Carrickfergus and Cork Harlequins in the All-Ireland T20 semis, with Eglinton or Brigade completing the line-up - they play today (SUN) in the North West decider.
The winners of the All-Ireland T20 will go on to represent Ireland in the European T20 competition in Spain.
LEINSTER SENIOR LEAGUE CUP FINAL
At Sydney Parade, Merrion beat YMCA by 6 runs
Merrion 150/7 (Jack Carty 59, Dom Joyce 43, John Anderson 28; James Forbes 2-18, Tom Anders 2-30)
YMCA 144/6 (20 overs; Tim Tector 41, Curtis Campher 33, Bobby Gamble 24).