Chris Strain reckons his table-topping Buffs showed real guts to knock Darvel off their perch.
David Syme's first half header was enough to win the battle of the early Premier pacesetters as Kilwinning leapfrogged the Vale at the summit.
But the hosts were made to sweat for the three points after surviving injuries to key men and a succession of second half scares.
Twice the woodwork came to their rescue after the break and goalkeeper Jamie Barclay had to pull off a stunning flying save to keep Darvel at bay.
But delighted Kilwinning boss Strain insisted his side were deserved victors as he hailed his squad's strength of character.
He said: "First half we were the better team.
"We rode our luck a wee bit in the second half but we deserved that luck because I think the game could have been out of sight for them. We had two or three chances when we were on top of the game.
"My overall reflection is we deserved to win the game. I think our character and guts got us through because we were running on empty with three injuries in the game and we had to make changes.
"I'm delighted. It shows we have the personnel to go on and win big games."
A bumper crowd, including a sizeable away support, crammed into Buffs Park for this hotly anticipated clash.
With just three minutes played, Kilwinning were forced to make a change after defender Kieran Wood picked up a knee knock, Tony Coutts replacing him at right back.
But the home side kept their focus and went on to dominate large spells of the first half.
Thomas Collins and Jordan Stuart both flashed efforts just past the post before Syme made the breakthrough in 35 minutes.
The former Kilmarnock defender rose highest to power Carlo Monti's inswinging corner kick past rooted Vale goalkeeper Lyle Avci.
The visitors were rocked and Avci twice came to their rescue before the break, first with a reflex save on the line to keep out a Ross Smith header, then with his hands to deny Collins after some trickery in the box.
Darvel had created virtually nothing in the opening 45 minutes but that changed after the break after manager Mick Kennedy tweaked his side's shape.
Early pressure had Buffs on the back foot and the visitors thought they'd levelled matters with a header from a corner kick to in 56 minutes only for the referee to spot a push and award the hosts a free-kick.
Kilwinning were finding opportunities harder to come by although Collins warmed Avci's gloves with a snap shot from seven yards just before the hour mark.
The action was primarily concentrated at the other end however, as the post came to Buffs aid before Barclay pulled off a brilliant stop to keep out a point black header.
Darvel looked certain to equalise in the closing stages when Ross Caldwell latched onto a rebound off the crossbar, but the former Hibs man blazed over from close range.
Kilwinning had to see out four minutes of stoppage time before the whistle blew for full-time.
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