Daniel Bell-Drummond’s half-century steered them to 173-8 before Middlesex secured their first T20 victory this summer at the fourth attempt.
Away skipper Stephen Eskinazi elected to field first on the used pitch and his team got a couple of early breakthroughs in front of a crowd of 4,010 at The Spitfire Ground.
England’s Zak Crawley took successive twos off the opening two balls but picked out cover off Tom Helm (2-24) as he departed early once again.
Next to go for Spitfires was Tawanda Muyeye, bowled for 12 from eight balls by Blake Cullen (1-46) to leave them 19-2 after two overs.
But that brought together Marcus O’Riordan and red-ball captain Bell-Drummond, who ensured the hosts raced to the 50-run mark in the fifth over with a combination of brute force and delicate touches to find the fence.
Kent looked well-placed on 78-2 at the end of the powerplay.
Their 66-run stand ended in the seventh over, though, when 26-year-old O’Riordan was trapped in front off Ryan Higgins (1-23) for a useful 28 from 11 balls.
But the home team moved beyond the 100-run mark in the 10th over and Bell-Drummond struck his seventh boundary off the next ball to move to his half-century in 28 balls.
Just two days on from his match-winning century against Somerset, skipper Sam Billings went for 10 this time. He was bowled by Luke Hollman (2-18), attempting a big switch-hit off his spin.
Bell-Drummond then went for a fine 60 from 38 balls to leave Spitfires 130-4. He picked out a scampering Leus du Plooy in the deep from the bowling of Hollman as he attempted to go down the ground.
Joey Evison was out in unusual fashion when he attempted a switch-hit and gloved Josh de Caires (1-20) onto his own stumps for four.
Middlesex had recovered well from the halfway mark, albeit a Denly four down the ground ended an 18-ball wait for a boundary in the 18th over.
That was followed by boundaries from South African overseas all-rounder Beyers Swanepoel – another from Denly – but Denly went off the first ball of the penultimate over.
The 38-year-old skied Helm up in the air and was caught by Eskinazi inside the ring for 28 from 22 balls.
Kent were stuttering to the end of their six-less innings and Swanepoel was well-caught for eight in the final over off Henry Brookes (1-34) by Eskinazi.
Australian overseas fast bowler Xavier Bartlett scampered two off the last ball.
Spinner Denly (1-21) surprisingly opened the bowling for Kent but it was a move which worked well.
He claimed his 50th T20 wicket to trap Martin Andersson for a five-ball duck to leave the visitors 1-1 after the first over.
Eskinazi soon found rhythm, however, and clipped Bartlett (3-34) over the legside boundary for the game’s first maximum.
As some wayward throws saw home fielders squander run-out chances, Middlesex had moved to 43-1 by the end of the powerplay.
The expensive Matt Parkinson (0-37) was brought onto bowl the seventh over but was sent for two sixes by Higgins.
Swanepoel (1-27) then got a much-needed breakthrough for Kent as he bowled 30-year-old Eskinazi went for 40 from 29 balls, the captain inexplicably attempting to scoop the ball over Billings.
But Middlesex looked in relative control at 84-2 at the halfway stage of the chase.
The 12th over saw them bring up their 100. South African du Plooy did so with a single from O’Riordan’s bowling (0-34) – a ball after he had sent him for a maximum.
Bartlett returned and instantly dismissed Higgins for 44 from 29 balls, trapping him in front.
And after du Plooy sent him for four through the legside, Bartlett, 25, claimed his revenge as he castled his stumps for 18 to leave the visitors 108-4.
Kent’s overseas players had largely done well and an economical Swanepoel over left the away side needing 45 runs from the final five overs.
Max Holden sent all-rounder Grant Stewart (1-18) for successive fours, only to scoop to Parkinson at short fine leg to go for 17 from 10 balls.
Parkinson returned to the attack at this stage but, again, proved costly. Wicketkeeper Jack Davies sent him for a six and a switch-hit four in the 17th over.
Middlesex appeared to have done enough as the game entered the last two overs, although Bartlett completed a good bowling display from himself with a third wicket. Davies was only able to pick out a back-pedalling Evison at mid-off for 23 off 16 balls.
Swanepoel at least ensured the match went to the final over but they had two runs to defend.
But Parkinson was dispatched for six over the legside by Hollman, who was 20 not out, as they finished 178-6 with four balls to spare. At the other end, de Caires finished unbeaten on seven.
Kent will take on holders Somerset at Taunton on Friday night before they face Gloucestershire at The Spitfire Ground next Sunday.
