Humphries – roared on by a sell-out crowd at the Oktoberhallen – celebrated his ninth European Tour crown with an impressive victory over Wales' number one.
Clayton drew first blood by winning the opening leg, but it was Humphries who was resurgent as he won six straight legs to take a commanding 6-1 lead, pinning checkouts of 142 and 130 in the second and seventh legs respectively.
The Llaneli-born star produced an excellent fightback of his own, winning four out of the next five legs, including a phenomenal 126 checkout on the bull after Humphries missed the bull himself on a 132 combination finish to go one away from victory.
However, Humphries denied Clayton the chance of a last-leg decider, defying the Welshman's late heroics by producing a 13-darter to clinch the title in Wieze.
Sunday March 22
ROUND THREE
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
Cristo Reyes 5-6 Ryan Joyce
QUARTERS
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
SEMIS
Neils Zonneveld 6-7 Jonny Clayton
Luke Humphries 7-2 Michael Van Gerwen
FINAL
Jonny Clayton 6-8 Luke Humphries