The reigning 11-times world champion claimed his sixth event title at Lower Trestles, his third on the bounce, in clean three-to-five foot waves.
Using a four-fin quad board, the American opted to surf smaller inside waves at the start of the final and never looked back from there, taking victory with a combined score of 16.50.
“I know I went out there feeling like I didn’t have anything to lose because Parko (Parkinson) was the form guy,” Slater said.
“He was pretty much the standout in every round. He schooled Medina (Gabriel Medina) yesterday somehow and was combo-ing everybody. I just figured I had to get myself on the best waves and let go a little bit, but it got really quiet out there.
"It was the first time something really felt like it went my way when they (the judges) took my priority away. By the time they announced it, Joel was above the wave and couldn’t catch it. That was the turning point for me.
"Every contest I’ve won, there’s some moment where things go my way."
Victory for Slater sees him claim third in the ASP ratings and the 40-year-old believes the win can be a turning point in his season.
“I knew that heat would either make or break me for the year,” Slater said. “I would have let Parko have those extra 2,000 points if he’d won and it would look very different on the ratings.
"It’s nice heading into Europe. I feel like I’ve had so many good years at Lowers and the pressure is really on every year to make the Final – I feel like it’s been like that since I’ve been on tour.
"It’s cool to win the 50th here. I won my first event as a pro here and it’s great to get this win.”
Parkinson, who had shown some great form on his run to the final at Trestles, consoled himself with what he saw as a satisfactory finish.
“A final is a good result,” Parkinson said. “Tahiti kind of hurt a lot. I felt like I was on a bit of a good one this week. It was all going well.
"Every time I paddled out, I had a lot of waves and Kelly (Slater) had those heats where he had no waves and I was thinking, ‘my mojo is stronger.’ Sure enough, the final was a slow one. It was one of those ones where you feel like you’re on point all week and Mother Nature just lets you down.”
Next stop on the tour is the Quiksilver Pro France, starting on September 28.
1 – Kelly Slater (USA) 16.50
2 – Joel Parkinson (AUS) 14.00
SF 1: Kelly Slater (USA) 17.27 def. Mick Fanning (AUS) 9.34
SF 2: Joel Parkinson (AUS) 18.26 def. Adriano de Souza (BRA) 13.43
QF 1: Mick Fanning (AUS) 17.60 def. Taj Burrow (AUS) 16.50
QF 2: Kelly Slater (USA) 15.17 def. Adrian Buchan (AUS) 11.93
QF 3: Joel Parkinson (AUS) 17.16 def. Jordy Smith (ZAF) 17.04
QF 4: Adriano de Souza (BRA) 12.60 def. John John Florence (HAW) 11.60
Round five results:
Heat 1: Mick Fanning (AUS) 12.90 def. Julian Wilson (AUS) 12.76
Heat 2: Kelly Slater (USA) 15.94 def. Jeremy Flores (FRA) 15.44
Heat 3: Jordy Smith (ZAF) 15.93 def. Josh Kerr (AUS) 9.57
Heat 4: Adriano de Souza (BRA) 18.30 def. Gabriel Medina (BRA) 9.57
ASP WCT top five (after Hurley Pro at Trestles):
1. Mick Fanning (AUS) 41,250 pts
2. Joel Parkinson (AUS)
3. Kelly Slater (USA)
4. John John Florence (HAW)
5. Adriano de Souza (BRA)