The DAMS driver lined up fourth, snatching second place off the road earlier than securing the lead from fellow Pink Bull junior Jak Crawford on lap two.
He held the lead till the tip, heading off challenges from Ralph Boschung, Jehan Daruvala and Victor Martins to take his third sequence win.
Martins put in an astonishing drive for ART to complete second, having lined up 10th as he begins on pole for Sunday’s characteristic race, whereas Daruvala settled for third.
With the entire discipline working the medium tyres, a superb begin from Iwasa noticed him leap Kush Maini and Campos team-mate Boschung off the road.
Martins was already up into seventh after the primary few corners, as he tussled with former F3 rival Ollie Bearman, who in flip despatched Jack Doohan vast at Flip 1.
Iwasa took the lead from Crawford regardless of a shortened DRS zone all the way down to Flip 1 on the second tour, and earlier than the primary security automotive was prompted by a spinning Zane Maloney, whose Rodin Carlin automotive got here to a cease on monitor at Flip 2.
Racing resumed on lap 5, with Boschung taking second from Crawford at Flip 2 as each Bearman and Daruvala gained locations. Additional again, Martins took sixth from Maini at Flip 13, with team-mate Pourchaire additionally passing the Campos rookie.
However the Alfa Romeo F1 reserve driver ended each his and Bearman’s races on lap seven whereas making an attempt to move Martins all the way down to Flip 1, outbraking himself and crashing into the facet of the Prema.
Victor Martins, ART Grand Prix
Photograph by: Method Motorsport Ltd
This prompted one other security automotive, taking the sphere by the pitlane because the stricken ART and Prema automobiles had been recovered, with Pourchaire approaching Bearman to apologise for the incident.
The motion resumed on lap 10, with Martins taking fourth from Crawford at Flip 1 as he continued his cost by the sphere.
Daruvala made it previous Boschung into second the next lap at Flip 27, with a fierce battle ensuing, the pair buying and selling locations a number of occasions earlier than the Indian driver emerged in entrance.
Martins then made it previous the Swiss driver for third earlier than setting concerning the main pair.
Daruvala briefly took the lead from Iwasa on lap 15 however ran vast and let the Japanese driver again by, permitting Martins to shut in.
The rookie then took second three laps from the tip, and regardless of closing in on the chief, needed to accept second however away from Daruvala.
Boschung completed fourth for Campos, with Maini in fifth and Frederik Vesti in sixth for Prema, whereas Doohan and Dennis Hauger rounded off the factors paying positions.
F2 Saudi Arabia – Dash race outcomes – 20 laps