Wednesday's winner Aspinall was chasing back-to-back victories after winning through to another decider at the Metrodome.
However, the former World Youth Champion battled back from 7-6 down to snatch victory and the £12,000 top prize.
Brown had knocked out World Champion Peter Wright with a 7-4 success, and he also defeated Jose de Sousa, Darren Webster, Luc Peters, Danny Baggish and Chris Dobey on the day.
Brown led 2-0 and 6-4 during the final, only to see Aspinall survive missed match darts in leg 11, finish 170 to level at six-all and then land double two to move ahead.
Brown took the tie to a deciding leg, and he was first to a finish before returning from a missed double top to secure the title on double ten.
"I'm absolutely over the moon," admitted Brown. "Nathan's a champion, he's a fighter but I thought to myself to stick with him, you get a chance with anyone.
"I think I've got luck on my side. I felt confident and it's a long time since I felt confident."
The Isle of Wight star's only previous senior PDC title had come in 2015 at a Players Championship in Coventry, but Thursday's win eases the pressure he was facing about potentially losing his Tour Card at the end of the year.
"Never give up," he admitted. "I can't tell you how many times over the last two years I wanted to pack it all away. My sponsors had faith in me, I kept plodding along and here we are.
"It's been awful, but darts is a marathon, not a sprint and you have to keep plugging away. I wanted to save my Tour Card and it's the only time I've ever probably believed in myself."
The week's third Players Championship event on Friday from 1200 BST will see the sport's biggest names battling it out for the £12,000 winner's prize at the Barnsley Metrodome.
2022 Players Championship 23 results
Alan Soutar 6-4 Ricardo Pietreczko
Ted Evetts 6-5 Danny Noppert
Nathan Aspinall 6-4 Andrew Gilding
Shaun Wilkinson 6-4 Rob Cross
Michael Smith 6-1 Niels Zonneveld
Peter Wright 6-4 George Killington
Keegan Brown 6-2 Danny Baggish
Chris Dobey 6-3 Dirk van Duijvenbode
Ted Evetts 6-2 Alan Soutar
Nathan Aspinall 6-1 Shaun Wilkinson
Peter Wright 6-3 Michael Smith
Keegan Brown 6-4 Chris Dobey
Nathan Aspinall 7-6 Ted Evetts
Keegan Brown 7-4 Peter Wright
Keegan Brown 8-7 Nathan Aspinall