The ding-dong affair went the distance, with Cool Hand Luke ultimately coming out on top against the Welshman in front of a packed crowd.
Humphries averaged 100.42 in the final, compared to Clayton's 98.25, while the Englishman also won the 180 battle 10-7 and Clayton had the highest checkout (120-91).
"I think I was a bit fortunate there - I started to feel the nerves at the end there, when I was 5-2 up I was trying too hard," Humphries told ITV after the win.
"When it went to 5-5, I'm not a negative person but I thought the game might have gone for me there.
"That was a really tough game, I played well in patches but for a period there Jonny was so dominant.
"I thought I could have played better, but I can't be too critical. I know I may complain a lot but that's because I know what my game can be like.
"To win trophies like these, even when you're not playing your best, it's amazing. Seven major titles now and I'm just three away from the great James Wade so to be so close to a player like him is incredible."
Not Clayton's day
Clayton admitted that "it just wasn't his day" and congratulated the victor.
"I had to dig in, he was running away with it.
"I always say this guy is a class act. I didn't give up and that's the good thing, I wanted to give Luke a great game and I think it was a great game.
"I thought at the end I might win but it just wasn't my day."
It was tight in terms of legs won, with Humphries egding it 14-13. On the doubles, Clayton was hitting 13 of 31 (42 per cent) and Humphries 14/47 (30 per cent).
Earlier in the evening, Clayton knocked out world champion Luke Littler in the quarter-finals and beat Dimitri van den Bergh 5-2 in the semi-finals, while Luke Humphries defeated Danny Noppert 5-2 en route to the final.
World number one Humphries earns £100,000 in prize money for winning the tournament.
