Humphries appeared to be in control, racing into a 4-1 lead, but Van Veen fought back to level the match at 4-4 after the Englishman missed a 25 checkout in the seventh leg.
The Dutchman then moved ahead 8-6, and what followed was a tense exchange of legs, with neither player able to establish more than a single-leg advantage.
In a gripping climax, Van Veen held his nerve to secure an 11-10 victory, capping a final that kept fans on the edge of their seats.
To reach the final, Van Veen had to navigate past compatriot Michael van Gerwen in the semi-finals and Northern Ireland's Daryl Gurney in the quarters.
As for Humphries, he edged an in-form Danny Noppert in his last-four clash, having earlier thrashed Luke Littler slayer James Wade earlier in the day.
Home hopes were dashed in the quarter-finals, when Germany's Ricardo Pietreczko fell to Noppert after a remarkable run in Dortmund.
Results
Quarter-finals
Joyce 5-10 Van Veen
Van Gerwen 10-7 Gurney
Noppert 10-5 Pietreczko
Wade 3-10 Humphries
Semi-finals
Van Veen 11-9 Van Gerwen
Noppert 8-11 Humphries
Final
Humphries 10-11 Van Veen