Fisk closed with a 3-under 67 in cloudy and breezy conditions at Hurstbourne Country Club on Sunday (Monday AEST) to match Pendrith at 16-under 264.
Played opposite the Scottish Open, the event was sanctioned by the PGA Tour and the European tour.
With the win, the 29-year-old Fisk gets into the PGA Championship but not the Masters next year.
Last October, he won the Sanderson Farms Championship in Mississippi for his first PGA Tour title.
Pendrith finished with a 65. The 35-year-old Canadian was trying to win for the second time on the tour.
"Kind of feel like all the work I've been putting in paid off," Fisk said.
"It's been a frustrating year trying to back up that first win. I've showed some pretty good signs of some solid golf, but haven't really had that opportunity to win a golf tournament that I've been kind of craving.
"It was unbelievable to get it done again."
On the final trip down the par-4 18th, Fisk made a 3-foot par putt after splitting the fairway and hitting to 28 feet. Pendrith drove into a fairway bunker, left his approach well short and missed a 10-foot par try.
On the first extra hole, Pendrith raced a 9-foot birdie try 4 feet past. They scrambled for pars on the second, with Fisk going from bunker to bunker and blasting out to 3 feet.
Canadian Ben Silverman and Aaron Wise were a stroke out the playoff. Silverman closed with a 66, and Wise shot 69.
Lucas Glover, atop the leaderboard after each of the first three rounds, had a 71 to tie for fifth at 14 under with Davis Chatfield (66) and Kristoffer Ventura (66).
Jackson Koivun closed with a 67 to tie for 10th at 12 under. He missed the cut last week in his professional debut.
No Australians made the cut for the ISCO Championship.
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