The 32-year-old followed up Saturday's win in Wigan with a dominant victory over Dimitri Van den Bergh.
Cullen edged past Rob Cross in the quarter-finals before overcoming world number one Gerwyn Price in the last four.
The Bradford star had it all his own way in the final though, beating his Dutch opponent 8-1 with an average of 102.34.
Cullen landed eight of his 13 chances to make a double and despite not making a single 180, he sealed four breaks of throw.
Cullen - after his Masters victory and reaching the final of night two of Premier League Darts - now has a total of 10 PDC titles to his name.
"I felt so much better today, felt a bit more comfortable going. Yesterday I feel like I was pulling a lot on the trebles but I seemed to be finishing well and today I got over the line," Cullen said.
"I'm playing well at the minute and even when I'm not playing well I can just turn it on. I've got that fear factor about me at the minute and things are going well. The best thing about it is, I'm not questioning myself anymore. It just seems to be working.
"Things are going well but it doesn't last forever it doesn't matter who you are," Cullen added about his current form. "While it's going well I'm going to take it as it comes. A few maybe questioned myself with the Premier League selection but I played decent in the Premier League and won back-to-back here on the weekend so I think I justified my selection," he added.
Results on Sunday
Gerwyn Price (104.59) 6-5 (102.61) Luke Humphries
Joe Cullen (103.17) 6-5 (99.52) Rob Cross
Krzysztof Ratajski (99.17) 6-5 (98.35) Dave Chisnall
Dimitri Van den Bergh (108.56) 6-5 (102.45) Daryl Gurney
Gerwyn Price (102.29) 5-7 (94.16) Joe Cullen
Krzysztof Ratajski (92.73) 4-7 (99.75) Dimitri Van den Bergh
Joe Cullen (102.34) 8-1 (95.06) Dimitri Van den Bergh