Driving for the Earl Bamber-supported Grove Motorsport squad, Campbell made the better start from the outside of the front row to beat polesitter Dries Vanthoor into turn one, and was never headed for the remainder of the hour-long encounter.
Turkey’s Ayhancan Guven also swept around the outside of Vanthoor into the first corner, the Belgian then running wide as he tried to fight back and losing a further two places to Italy’s Mirko Bortolotti and Germany’s Luca Stolz.
Vanthoor reclaimed fourth from Stolz by the end of the opening lap, as Campbell opened up a 1.8-second lead over fellow Porsche 911 driver Guven.
That margin was briefly reduced to under a second before the Australian started to break clear, with Guven falling into the clutches of Bortolotti and Vanthoor approaching the 15-minute mark.
Bortolotti then snatched second on the inside of turn six, with Guven eventually ordered to let Vanthoor through having run off the circuit during a hard-fought defence of third place.
The squabble allowed Campbell to extend his advantage at the front to over 5s, while Vanthoor upped the pace to close in on Bortolotti.
The Lamborghini and Audi drivers remained nose-to-tail in the second half of the race, while also chipping away at Campbell’s lead - the margin reduced to 1.6s by the chequered flag.
Vanthoor had to settle for third behind Bortolotti after making a small mistake late on.
Stolz eventually caught Guven, who lost touch with the top three. After a close battle for several laps, the Mercedes driver capitalised on a mistake to move by and come home in a lonely fourth.
Guven was the cork in the bottle in a battle for fifth in the closing stages, with Tristan Vautier (France) Michael Benyahia (Morocco) and Daniel Juncadella (Spain) all queuing up behind.
Benyahia made a couple of late lunges up the inside of Vautier, the second of which ended in contact and retirement after damaging his McLaren 720S, while Vautier also lost ground.
Guven held off Bruno Baptista for fifth at the finish, the Brazilian having made a final-lap overtake on Juncadella, who was then demoted to ninth by a 5s track limits penalty.
That promoted Chinese Taipei’s Evan Chen to seventh and Vautier to eighth, while Switzerland’s Yannick Mettler rounded out the top-10.