The Steelbacks stunned the Vikings on the opening night of the NatWest T20 Blast as Graeme White hit the fifth ball of the last over for four to snatch a dramatic three-wicket win.
Yorkshire seemed on course to beat the holders when Ryan Sidebottom ran out Matt Spriegel to leave Northamptonshire needing nine to win from only four balls.
But Ben Duckett, a wicketkeeper who was a team-mate of Will Rhodes and several other Yorkshire players in the recent Under-19s World Cup, launched Sidebottom for a crucial six over long off before White hit the winning runs.
The Vikings struggled to get going early in their innings, after Andrew Gale had won the toss and chosen to bat first on a sunny Leeds evening.
Gale fell to the second ball from Northamptonshire’s new overseas signing, the New Zealand seamer Ian Butler, as Scotland’s one-day captain Kyle Coetzer took an excellent catch running in from long on.
Kane Williamson cracked a couple of boundaries before being run out by a direct hit from David Willey, the man of the match in last year’s final, at backward point. Then Joe Root was lbw trying to sweep Azharullah, and the score was 37 for three.
Like Root, Gary Ballance showed promise but was unable to deliver a big score, and he also fell sweeping, with the ball lobbing up to short fine leg.
Adil Rashid and Jonny Bairstow put on the best stand of the innings thus far, and Bairstow launched White for the first six of the innings over long on.
But when they fell to consecutive deliveries from Butler, Yorkshire were in real trouble at 87 for six.
It was down to Bresnan and Plunkett that the Vikings had a competitive total to defend, as they added 64 inside six overs.
Plunkett fell in the 19th over, a fourth victim for Butler after hitting 36 from 22 balls. Bresnan powered on to an unbeaten 34 from 21 balls with two cleanly struck sixes.
The Steelbacks made a solid start to their reply with the South African opener Richard Levi looking dangerous. He hit Plunkett’s first ball for six but the in-form all-rounder hit back immediately to have him coolly caught by Jack Brooks at long leg.
Brooks was in the action again next ball, running out the Northants captain Kyle Coetzer before he had faced a ball with a direct hit from backward point.
Willey continued to threaten, punishing Adil Rashid in what turned out to be his only over with two sixes and a four to the short legside boundary.
But Yorkshire turned to Richard Pyrah, so often their unsung hero, from the Rugby Stand End, and yet again he did not disappoint.
He had Willey launching to long off, where Ballance took the catch, and when Plunkett bowled Rob Newton in the next over, the Steelbacks had been pegged back to 82 for four.
Steven Crook and Duckett then added 42 for the fifth wicket before Pyrah struck again with the crucial wicket of Crook, lbw in his last over with the excellent figures of two for 21.
Sidebottom then delivered a mean 18th over in which he bowled Butler, only to be denied at the last.
With each county playing 14 games at the group stage this season, there is still plenty of time for the Vikings to bounce back in their bid to reach finals day at Edgbaston – which is also the venue for their next group match next Friday night against the renamed Birmingham Bears.