As American Wyndham Clark held off Irish superstar Rory McIlroy to claim the PGA Tour's second and penultimate play-off event in Missouri, Scott sealed his place at the season-ending showpiece with his own brilliant final round.
On a day of tough scoring at the Bellerive Country Club, Scott closed with a three-under-par 67 to finish in a tie for 16th at six under.
Scott, who is 28th in the FedEx standings, will join fellow Australian Min Woo Lee in the hunt for the $US10 million winner's cheque at next week's season-ending championship in Atlanta.
The former world No.1 will be contesting his 14th Tour Championship, 20 years after winning one of golf's most prestigious trophies.
Lee will be making his Tour Championship debut after qualifying for the elite 30-man field in 20th position in the season-long points race.
The 28-year-old tied for 47th in St Louis at two over after posting a final-round 71 as Clark held his nerve down the stretch to claim the spoils.
After starting the day with a five-stroke buffer, the two-time US Open champion relinquished his huge lead with three bogeys in his first 10 holes.
But he steadied with a hat-trick of birdies on 16, 17 and 18 as McIlroy's challenge ended with a gut-wrenching bogey six on the second-last hole.
With a final-round 70, Clark won by three shots at 17 under, with fellow American Patrick Cantlay (68) snatching second.
McIlroy (69) was solo third at 13 under.
"I think it shows that I'm one of the best players in the world," Clark said after capturing his third title of the year.
"I know everyone maybe gives me a hard time and roots for other people, but I feel like I've kind of come into my own. Three wins in one season is my best year yet."
Cantlay, who came in at No.43 in the FedEx Cup, showed plenty of moxie.
Four times he bounced back from a bogey with a birdie, closing with three birdies to also be among the top 30 to advance to the Tour Championship.
"I'm coming to a golf course that I played really well at next week," said Cantlay, who won at East Lake in 2021 to claim the FedEx Cup.
"So I'm really pleased with where my game is at and I think I'm trending in the right direction."
Also moving into the top 30 was another American, Gary Woodland, who pulled within one shot of the lead until topping his tee shot into a creek on the ninth hole on his way to a double bogey.
He closed with nine straight pars and fought back tears as he returns to the Tour Championship for the first time since 2019 after recovering from brain surgery three years ago.
He said Saturday, when he was in the final group, took a lot out of him with the noise, the energy and the drones that triggered the kind of brain activity he tries to calm.
On Sunday, he tried to embrace it and pulled through with a 69 to tie for fourth.
"I tried to enjoy it," Woodland said.
"Outside of topping a ball ... I haven't done that for a long time. I'm just really proud."
With The AP
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