The world number two, who had endured a relative lull by his own standards in recent months, surged into a commanding early lead before resisting a fight-back to secure his ninth European Tour crown.
Clayton struck first in the final, but Humphries swiftly seized control, reeling off six consecutive legs to move 6-1 ahead. Checkouts of 142 and 130 underlined a ruthless spell that looked to have settled the contest.
Yet Clayton refused to relent. The Welshman clawed his way back, winning four of the next five legs and producing a superb 126 finish on the bull to close the gap, after Humphries had squandered an opportunity to move within one of victory.
But Humphries, who has built his reputation on composure under pressure, halted the surge with a critical 13-darter to close out the match and deny a deciding leg.
“I put myself under pressure, but it’s really nice to get that winning feeling again," said Humphries, after winning his first title on the European Tour since September 2025.
“Usually in those circumstances, I probably close the game out a lot better, but when you’re not winning as much, it becomes harder, and you feel the nerves.
“Jonny is one of the most underrated dart players in the world. You cannot shake him off, and big credit to him for fighting back, but this means a lot to me.”
Earlier in the day, Humphries opened his Finals Day with a 6-1 victory over Jermaine Wattimena, averaging comfortably above a ton, before surviving a last-leg encounter against Chris Dobey.
His most emphatic statement, however, came in the semi-finals, where he dismantled Michael van Gerwen 7-2 -- a result that extinguished the Dutchman’s hopes of adding yet another Belgian title to his collection.
Clayton overcame Poland’s Sebastian Bialecki en route to the final, before edging past England’s Ross Smith in a deciding leg, and then producing one of the performances of the tournament to sweep aside home favourite Andy Baetens 6-1.
In the semi-finals, Clayton survived four match darts to deny Niels Zonneveld in another last-leg decider, sealing his place in the final.
"I thought I was going home early when I was 6-1 down," joked Clayton, after his defeat to Humphries.
"Luke gave me a few chances. I got back in the game, but he missed a lot of doubles, to be fair.
"Luke is a great dart player, a great asset to darts, and I'm proud to be part of this era of darts with these fantastic fans.
"I'm trying my best. When you've got to face the likes of Luke week in, week out, it's difficult, but I'm still a part of it, so I'm proud of myself.”
Littler crashes out
Zonneveld, the surprise package of the weekend, had earlier produced one of the moments of the tournament in dispatching world number one Luke Littler.
Littler started strong, powering into a 3-1 lead, but failed to win consecutive legs after that, eventually falling to an unlikely 6-5 loss.
Both players enjoyed high-scoring averages, with Littler hitting 103.2 and Zonneveld just behind him at 101.58.
The result was a shock after Littler's impressive opening match on Saturday, in which he defeated Boris Krcmar 6-2.
Zonneveld proved too much for the world champion on Sunday morning, though, with the world number 39 hitting a 147 checkout to win the match.
Results
Round of 16
Niels Zonneveld 6-5 Luke Littler
Danny Noppert 6-5 Ryan Searle
Jonny Clayton 6-5 Ross Smith
Andy Baetens 6-5 Martin Schindler
Luke Humphries 6-1 Jermaine Wattimena
Chris Dobey 6-3 Kim Huybrechts
Michael van Gerwen 6-5 Daryl Gurney
Ryan Joyce 6-5 Cristo Reyes
Quarter-finals
Niels Zonneveld 6-3 Danny Noppert
Jonny Clayton 6-1 Andy Baetens
Luke Humphries 6-5 Chris Dobey
Michael van Gerwen 6-4 Ryan Joyce
Semi-finals
Jonny Clayton 7-6 Niels Zonneveld
Luke Humphries 7-2 Michael van Gerwen
Final
Luke Humphries 8-6 Jonny Clayton