The DAMS driver lined up fourth, snatching second place off the line before securing the lead from fellow Red Bull junior Jak Crawford on lap two.
He held the lead until the end, fending off challenges from Ralph Boschung, Jehan Daruvala and Victor Martins to take his third series win.
Martins put in an astonishing drive for ART to finish second, having lined up 10th as he starts on pole for Sunday’s feature race, while Daruvala settled for third.
With the whole field running the medium tyres, a brilliant start from Iwasa saw him jump Kush Maini and Campos team-mate Boschung off the line.
Martins was already up into seventh after the first few corners, as he tussled with former F3 rival Ollie Bearman, who in turn sent Jack Doohan wide at Turn 1.
Iwasa took the lead from Crawford despite a shortened DRS zone down to Turn 1 on the second tour, and before the first safety car was prompted by a spinning Zane Maloney, whose Rodin Carlin car came to a stop on track at Turn 2.
Racing resumed on lap five, with Boschung taking second from Crawford at Turn 2 as both Bearman and Daruvala gained places. Further back, Martins took sixth from Maini at Turn 13, with team-mate Pourchaire also passing the Campos rookie.
But the Alfa Romeo F1 reserve driver ended both his and Bearman’s races on lap seven while attempting to pass Martins down to Turn 1, outbraking himself and crashing into the side of the Prema.
Victor Martins, ART Grand Prix
Photo by: Formula Motorsport Ltd
This prompted another safety car, taking the field through the pitlane as the stricken ART and Prema cars were recovered, with Pourchaire approaching Bearman to apologise for the incident.
The action resumed on lap 10, with Martins taking fourth from Crawford at Turn 1 as he continued his charge through the field.
Daruvala made it past Boschung into second the following lap at Turn 27, with a fierce battle ensuing, the pair trading places several times before the Indian driver emerged in front.
Martins then made it past the Swiss driver for third before setting about the leading pair.
Daruvala briefly took the lead from Iwasa on lap 15 but ran wide and let the Japanese driver back through, allowing Martins to close in.
The rookie then took second three laps from the end, and despite closing in on the leader, had to settle for second but clear of Daruvala.
Boschung finished fourth for Campos, with Maini in fifth and Frederik Vesti in sixth for Prema, while Doohan and Dennis Hauger rounded off the points paying positions.
F2 Saudi Arabia - Sprint race results - 20 laps
|2||Victor Martins||ART Grand Prix||0.700||0.700|
|3||Jehan Daruvala||MP Motorsport||1.100||0.400|
|4||Ralph Boschung||Campos Racing||1.900||0.800|
|5||Kush Maini||Campos Racing||2.500||0.600|
|6||Frederik Vesti||Prema Powerteam||2.900||0.400|
|7||Jack Doohan||Invicta Virtuosi Racing||3.300||0.400|
|8||Dennis Hauger||MP Motorsport||4.500||1.200|
|9||Jak Crawford||Hitech Pulse-Eight||4.500||0.000|
|10||Roy Nissany||PHM Racing by Charouz||6.400||1.900|
|12||Isack Hadjar||Hitech Pulse-Eight||7.600||0.800|
|13||Enzo Fittipaldi||Rodin Carlin||8.300||0.700|
|14||Juan Manuel Correa||Van Amersfoort Racing||13.100||4.800|
|16||Richard Verschoor||Van Amersfoort Racing||13.700||0.000|
|18||Brad Benavides||PHM Racing by Charouz||20.500||6.300|
|19||Amaury Cordeel||Invicta Virtuosi Racing||35.400||14.900|
|Oliver Bearman||Prema Powerteam|
|Theo Pourchaire||ART Grand Prix|
|Zane Maloney||Rodin Carlin|
|View full results|