This year's Masters champion was far from his best in the early rounds, but turned on the style when it mattered most and powered to an 8-2 victory over William O'Connor in the final.
The 33-year-old not only secured his third career European Tour title but also took home £25,000 in prize money.
Cullen had battled past Martin Lukeman in Saturday's second round, and saw off Jim Williams in Sunday afternoon's third round to continue his challenge.
He then overcame Rusty-Jake Rodriguez 6-4 in the quarter-finals and survived three missed match darts from Dave Chisnall during their semi-final, before producing a 12-darter to complete a 7-6 victory.
Cullen's most dominant display came in the final, as he claimed the opening five legs without reply, twice punishing missed doubles from O'Connor whilst also posting a 13-dart leg, two 14-darters and a 100 finish.
The World Series star moved 6-2 up before producing an 11-darter to go within one leg of the title. O'Connor had opportunities to stay in the match, though four misses allowed Cullen to claim the prize on double eight.
"I didn't expect to come to Budapest and win, but I'm over the moon," said Cullen.
"In my first three games I was terrible and a bit lucky to get through all three of them. Then I turned it on a little bit in the semis and I think I was pretty decent in the final.
"I kept Willie at bay, because I'd seen how well he played over the weekend and that's what I had to do."
Photo Credit: Kais Bodensieck/PDC Europe