Seekkuge Prasanna secured instant hero status as he hit his first ball as a Steelbacks player for six to earn a five-wicket success at Leicestershire Foxes.
The Sri Lankan all-rounder, who had earlier claimed one for 21 in a fine bowling display, stepped up with Northants needing two runs to win from the final two balls.
And he showed no signs of nerves as he casually placed Ben Raine’s delivery beyond the boundary ropes before sharing an embrace with Ben Duckett to celebrate the win.
Duckett had finished unbeaten on 37 as he showed his class with a display that helped to steer his team home.
Earlier, Leicestershire had made their way to 178 for five, with a big final over, which was worth 23 runs, helping them pose a good total.
Umar Akmal, who was dropped on 26 by Richard Levi, was the main provider of runs with an unbeaten 52, while five Northants bowlers took a wicket apiece.
In the reply, Levi and Adam Rossington got the Steelbacks off to a flying start, which saw them register 75 runs from the powerplay.
Rossington fell for 23, but Levi pushed on to earn his eighth T20 half-century for Northants, eventually departing for 61 from 29 balls.
A rain delay ruined the away side’s rhythm and the Foxes fought back, but Prasanna had the final word with his nerveless six.
Northants had headed into their T20 opener in confident mood, having reached the final of the competition in 2015.
Rory Kleinveldt got the new campaign up and running as he opened the bowling for the Steelbacks.
But the South African was to ship an early boundary apiece to the opening pair of Mark Pettini and Mark Cosgrove.
Olly Stone tightened things up in the second over, conceding just five runs, but the Foxes were soon back in the boundaries in the third over, with Pettini playing some nice shots.
Kleinveldt had been costly, conceding 27 runs from his first two overs, and Northants needed to respond to the Leicestershire aggression.
But Cosgrove proceeded to plunder the home side’s first six, lifting Stone over third man, and there was still no answer from the Steelbacks.
Muhammad Azharullah was introduced in a bid to stem the tide after four overs that had gone for 45 runs, and he almost got the breakthrough as Pettini saw one drop just short of Josh Cobb at short fine leg.
The powerplay finished with Leicestershire having racked up 11 fours and one six, with the home side boasting an impressive tally of 62 without loss.
But Azharullah was to have an effect in his second over, dismissing Cosgrove for 27 as the Steelbacks got the wicket they desperately wanted.
And the next one wasn’t to be too far away as Prasanna, who had been hard to get away in his first over, struck in with his ninth ball in Northants colours.
Kevin O’Brien was the victim as he was caught by Cobb at long off for 14, with the Foxes 84 for two at the halfway stage.
The Steelbacks were starting to pull it back and Graeme White trapped Pettini LBW for 43 as Leicestershire were left on 97 for three with eight overs to go.
Akmal then escaped twice after playing a couple of dubious shots before Niall O’Brien was deceived by Kleinveldt’s slower ball, with the batsman firing the ball into his stumps to depart for 13.
With five overs to go, the Foxes had a decent platform at 119 for four, and Akmal got another big reprieve as Levi dropped a catch he would have felt he should have taken off Azharullah.
Debutant Prasanna started his stay at the Steelbacks with strong figures of one for 21 from four overs as the Foxes were left chasing their tails late on at 143 for four from 18.
Stone was given the task of bowling the final over, but he saw the ball roll relentlessly across the boundary ropes.
He did get rid of Tom Wells for 21 thanks to a fine catch from Rob Keogh, but the over was to go for a massive 23 runs, as the Foxes finished on 178 for five with Akmal unbeaten on 52 from 32 balls.
The Steelbacks’ reply started in stylish fashion, with Levi and Rossington looking calm and composed as they chalked up some early boundaries.
The fourth over, from Raine, brought a huge 20 runs, with the elegant Levi and ruthless Rossington dishing out some severe punishment to silence the home support.
But Rossington just tried to force it a bit too much in the fifth over and paid the price as he top edged a Rob Taylor delivery and was caught at point for 23.
Levi was still there though and he reached his 50 from just 20 balls thanks to back-to-back fours, leaving the Steelbacks on 75 for one after a superb powerplay period.
Cobb came and went as his return to his former stomping ground was ended prematurely by Jigar Naik, who dismissed trapped the Northants man LBW for four.
And the Steelbacks soon suffered another blow as Raine got his revenge on Levi, dismissing the big South African for 61 from 29 balls as Pettini took the catch.
The rain then interrupted proceedings and with two overs lost, the Steelbacks, who were 111 for three, found themselves needing 53 runs to win from the final seven overs.
The majority of the crowd had headed home, feeling their Friday night would be better spent elsewhere with their team’s chances having seemingly faded with the light.
But the Foxes fought hard after the resumption and they made a game of it with some tight bowling.
Duckett did manage to relieve some pressure with a couple off fours from a Neil Dexter over, leaving the Steelbacks needing 31 from the final four overs.
Steven Crook saw his tricky time in the middle come to an end via a Taylor run out in the 16th over, pushing skipper Alex Wakely into the fray in the final stages.
Duckett was still ticking along nicely at the other end, timing his shots well and picking up crucial boundaries.
Wakely was fortunate to see a ball keep low and nutmeg wicketkeeper Niall O’Brien to go four four before the captain chipped one towards extra cover, who just couldn’t get there.
The Steelbacks needed seven runs from the final six balls and Wakely, who had four from eight, was on strike against Raine.
But Wakely was to go from the first ball as he found Taylor in the deep, leaving Duckett on strike with seven still needed.
Duckett immediately swept the ball for four to ease some tension, but when his drive his the stumps at the other end to turn a four into a single, Prasanna was left on strike with the Steelbacks still requiring two from two.
But the Sri Lankan refused to feel any nerves and he stepped up to hit Raine for six in his first ball faced as a Steelbacks player.
It was a huge moment for Prasanna and he and Duckett shared a joyous embrace as the away side celebrated a narrow victory.
Leicestershire Foxes: Pettini (c), Cosgrove, K O’Brien, Akmal, N O’Brien, Dexter, Wells, Taylor, Raine, McKay, Naik.
Northants Steelbacks: Levi, Cobb, Wakely (c), Duckett, Prasanna, Rossington, Crook, Kleinveldt, White, Stone, Azharullah.