Mostert led an Audi one-two in qualifying for the second round of the TCR Australia season, the gap back to teammate Luke King just under three-tenths.
That was after he was narrowly edged by HMO Hyundai driver Nathan Morcom in the first part of qualifying.
It’s the Bathurst 1000 winner’s first pole TCR pole, coming in just his second start in the category.
“From the first session to the second part we tuned the car up a little bit and made it heaps better,” said Mostert. “It was a little loose out the gate, but I’m pretty happy to get the pole. We’ll see how we go in the races.”
Lee Holdsworth (ASM Alfa) was next best behind the Audis, his gap to Mostert just over four-tenths, followed by fellow Alfa driver Michael Caruso and Ben Bargwanna (GRM Peugeot).
John Martin led the way for the Wall Honda squad in sixth, while Morcom slipped back to seventh after topping the first part of the session.
Aaron Cameron (GRM Peugeot) was eight, Josh Buchan (HMO Hyundai) ninth and Tony D’Alberto (Wall Honda) 10th.
In S5000 qualifying James Golding took a comfortable pole, the GRM driver half a second clear of the field.
Tim Macrow was best of the rest ahead of points leader Thomas Randle, Nathan Herne and Luis Leeds.
The session featured a brief stoppage after Antonio Astuti ran wide at the final corner and brushed the wall on his first lap.