The Frenchman, who started in seventh for ART Grand Prix, had a great start and made it past a startline crash from Prema's Dennis Hauger and Jack Doohan (Virtuosi) to claim fifth by the first corner.
After pitting for medium tyres, he passed Campos Racing's Ralph Boschung for net second place on lap 19, before Nissany crashed out two laps later, handing Pourchaire the lead, which he held onto until the chequered flag.
