It was a first tournament win for the 39-year-old since he opened up about his mental health struggles in January.
Belgium's Brecel hit back from 4-1 down to level the match at 4-4 in the evening session.
Selby regained a two-frame lead with breaks of 51 and 61 before Brecel, who had yet to pass 50, hit the final's first century, a 122, to make it 6-5.
Selby won the next two before Brecel had a chance for a maximum, taking all the reds only to miss a tricky 15th black.
But Selby wrapped up the victory with a break of 87 before welling up as he thanked wife Vikki afterwards.
"I think for me this has to go down as the biggest achievement, back from where I was in January," he told Eurosport.
"I've been suffering for a few years silently. Only Vikki and my family really knew and it's been tough, from January, trying to get myself back on my feet.
"It's not been easy, probably the biggest challenge of my life, so coming out here and winning a tournament is incredible really.
"There's not enough words I can say about Vikki. If it wasn't for her I definitely wouldn't be stood here today, that's for sure."