The All-Ireland T20 went to a super over for the second year in succession, with Lisburn prevailing in a drama filled day.
Batting first, Leinster looked in disarray at 52 for 5 at the midway point of their innings.
Tom Johnson and Saqib Bahadur totally transformed things with an 118-run partnership from only 50 balls to get their side up to an imposing 192 for 7.
Johnson top-scored with 75 from only 30 balls (5 fours, 7 sixes), while Bahadur's 32-ball 61 not out included 9 fours and a six.
Josh Manley (2-20) was by some distance the best of the Lisburn attack.
The NCU side raced out of the traps with an opening stand of 83 in just 50 balls between Indian overseas professional Faiz Fazal and Jonny Waite laying the perfect platform.
Waite's uncomplicated but highly effective style seeing him thump 5 fours and 4 sixes in a 24-ball 48.
Nigel Jones went cheaply, but Fazal kept finding boundaries when they were needed to reach 88 off 50 balls (8 fours, 4 sixes).
As he and skipper Neil Whitworth added 83 in 9 overs, it left the equation as 24 needed off 19 balls with 8 wickets in hand.
However, Fazal's dismissal saw panic set in and with two balls left, Lisburn still needed 7. Whitworth cleared the ropes at deep square to tie the scores, but was then well caught at short third man to send the game into extra time.
Fazal once again the hero as the left-hander took Bahadur apart with a four, followed by three consecutive sixes.
Set 24 to win, Leinster could only manage 9 with Josh Manley taking two wickets.
A first All-Ireland T20 for Lisburn who will now be Ireland's representative at the European T10 Champions League in Spain next year.
National T20 Cup Final: Leinster lost to Lisburn by 14 runs in a Super over
Phoenix Park, Dublin, 25 August.
Leinster 192/7 (20 overs; Tom Johnson 75, Saqib Bahadur 61*, Monil Patil 19; Josh Manley 2-20, Matthew Humphreys 2-38, Neil Whitworth 2-40) and 9-2 (1 overs; Josh Manley 2-9)
Lisburn 192/7 (20 overs; Faiz Fazal 88, Jonathan Waite 48, Neil Whitworth 35) and 23-2 (1 over; Faiz Fazal 22)