The Japanese DAMS driver took pole position on Friday before taking victory ahead of the 2022 champion in Sunday’s feature race.
Despite better overtaking attempts from the MP Motorsport driver in the closing laps, Iwasa held on to take his first win since the French Grand Prix.
Sargeant now looks set to graduate to Formula 1 with Williams next season after a fifth-place finish was enough to secure him the requisite super license points, as he sat fourth in the drivers’ standings behind Lawson.
Drugovich’s second place secured MP Motorsport the teams’ title, with Carlin finishing second thanks to Liam Lawson’s third place.
Polesitter Iwasa led from the start and despite briefly slipping behind second place and teammate Roy Nissany, the Japanese driver held onto the lead into the opening laps.
Theo Pourchaire lost a few places in the initial 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 wide at Turn 9, with Ralph Boschung spinning after contact with Juan Manuel Correa, returning to F2 with Van Amersfoort Racing.
After a brief Virtual Safety Car stint, Pourchaire jumped over Hauger on the restart to take fourth into Turn 3.
Drugovich then passed Nissany for second into turn 9 on lap seven, as behind them Hauger and Lawson were the first to stop. Lawson emerged ahead of the 2021 FIA Formula 3 champion to take third.
Iwasa then pitted from the lead, with Pourchaire joining him to take the medium Pirelli compound before the Frenchman emerged behind Lawson and Hauger despite a battle with the Norwegian driver.
Drugovich, Nissany, Sargeant and Frederik Vesti pitted on lap nine, with Drugovich emerging in net second behind Iwasa, with Lawson and Hauger in third and fourth.
By lap 12, Jack Doohan was leading through those yet to stop, with the Virtuosi driver building a commanding lead over Marcus Armstrong while Iwasa led those who had pitted as they made their way through the field.
Pourchaire made an unsuccessful attempt to pass Hauger at Turn 6 several laps later, with more attempts at Turn 9 before finally passing him on Lap 22 when the Prema driver went off.
Doohan finally pitted on lap 25 and looked ready to use his fresh tire advantage to push his way through the field.
But as he rejoined the track, his left front tire came off, flew across the track, forcing several drivers to take evasive action.
He was forced to retire from the race, which dropped him to sixth in the drivers’ standings.
The VSC were briefly deployed for the stewards to retrieve the rogue wheel, and once racing resumed Drugovich looked ready to pounce on Iwasa, though the Red Bull junior put up a strong fight against the newly crowned champion.
With four laps to go, Sargeant finally passed Nissany for sixth on the outside of Turn 9.
Pourchaire then suffered a terminal mechanical problem, 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 for retirement.
Amaury Cordeel finished sixth for VAR, with Richard Verschoor seventh for Trident.
The Hitech pairing of Juri Vips and Armstrong finished eighth and ninth, with Nissany rounding out the points.