The Japanese DAMS driver took pole on Friday before claiming victory ahead of the 2022 champion in Sunday’s feature race.
Despite the MP Motorsport driver’s best attempt to pass in the final laps, Iwasa held on to take his first win since the French Grand Prix.
Sargeant now looks set to finish in Formula 1 with Williams next season after a fifth-place finish was enough to earn him the necessary superlicence points as he sits fourth in the drivers’ standings behind Lawson.
Drugovich’s second-place finish earned MP Motorsport the teams’ title, with Carlin finishing second courtesy of Liam Lawson’s third-place result.
Pole-sitter Iwasa led from the off and despite briefly slipping behind second-place starter and teammate Roy Nissany, the Japanese driver led the opening lap.
Theo Pouchaire lost several places in the opening melee, with the ART driver falling behind Drugovich and Prema’s Dennis Hauger.
Yellow flags were waved briefly on the opening lap after MP’s Clement Novalak went into Turn 9, with Ralph Boschung spinning after contact with Juan Manuel Correa, who returns to F2 with Van Amersfoort Racing.
After a brief Virtual Safety Car period, Pourchaire dethroned Hauger on the restart to go into turn four at Turn 3.
Drugovich passed Nissany for second at Turn 9 on lap seven as behind them, Hauger and Lawson were the first of the soft tire runners to stop. Lawson edged ahead of the 2021 FIA Formula 3 champion to run third.
Iwasa took the lead, with Pouchaire to take the medium compound Pirelli before the Frenchman emerged behind Lawson and Hauger despite battling with the Norwegian driver.
Drugovich, Nissany, Sargeant and Frederik Vesti pitted on lap nine, with Drugovich taking second behind Iwasa, with Lawson and Hauger in third and fourth.
On lap 12, Jack Doohan took the lead of the pitstops, with the Virtuosi driver building a commanding lead over Marcus Armstrong while Iwasa led the pitters as they moved through the field.
Pourchaire failed to pass Hauger at Turn 6 a few laps later, with further attempts at Turn 9 before he finally passed on lap 22 as the Prema driver ran wide.
Doohan finally pitted on lap 25 and looked set to use his new tire advantage to cut through the pack.
But as he rejoined the track, his left front tire came off, flying back onto the track and forcing several drivers to take evasive action.
He was forced to retire from the race, dropping him to sixth in the drivers’ standings.
VSC was briefly deployed for the marshalls to recover the rogue wheel, and once the race resumed, Drugovich looked set to jump Iwasa, though the Red Bull junior defended strongly from the recently crowned champion.
Four laps from the end, Sargeant finally passed Nissany for sixth place out of Turn 9.
Pourchaire then suffered a terminal mechanical issue, dropping him down the order and leaving ART unable to clinch the teams title.
Hauger finished fourth after his battles with the Frenchman, with Sargeant promoted to fifth by retirement.
Amaury Cordeel finished sixth for VAR, with Richard Verschoor seventh for Trident.
The Hitech pair of Juri Vips and Armstrong finished eighth and ninth, with Nissany rounding off the points.