The Tigani Motorsport pair combined to lead from lights to flag, with Pires holding off a hard-charging Brad Schumacher in the early laps.
The win follows a missed chance at consecutive podiums during Round 1 due to contact from Mark Rosser in the closing stages of the event.
Leitch and Pires become the third different winners in the first three races of the season.
Schumacher was quick in the opening laps, however suffered from understeer through the fast Turn 8, 9, 10 complex, spinning off the road.
The Audi veteran fell back through to the back end of the top five, before handing over to Broc Feeney at the mid-point of the race.
Despite the Evans/Schutte Ferrari having an extra 10 seconds of pit stop time from the previous round, a slow left rear tyre change saw Feeney emerge behind Evans in fourth spot.
Secure your spot today.
Shane Smollen was given a drive through penalty in the early laps following a procedural error prior to the race start.
Following the pit stop cycle, Leitch emerged in the lead, with Randle a little over two seconds behind.
As the pair ran away at the front, the battle in the middle of the top 10 heated up.
Ryan Wood and Jayden Ojeda set about chasing down Will Davison for fifth position, but the Ferrari held ground in the closing laps.
Leitch led home Randle to give Pires his first GT World Challenge victory, with Evans/Schutte hanging on to third.
Feeney/Schumacher came home fourth, while Davison held on to fifth in the Ferrari shared with Renee Gracie.
Wood/Steve Brooks were sixth ahead of Ojeda/Lucchitti.
Garnet Patterson brought the third Team BRM entry shared with JP Drake home in eighth, ahead of Oscar Targett and Smollen.
Josh Buchan/Cameron Campbell rounded out the top 10 following a grid penalty after an incident in qualifying.
Paul Stokell/Matthew Stoupas came home in 12th position outright to win the Trophy Class.
GT World Challenge Australia returns on Sunday for Race 2 at 2:10pm ACST.
Results: GT World Challenge Australia powered by AWS The Bend, Race 1
| Pos | Num | Drivers | Team | Car | Class |
| 1 | 44 | B.Leitch/S.Pires | Geyer Valmont Racing by Tigani | Mercedes-AMG GT3 | PA |
| 2 | 268 | T.Randle/M.Rosser | Castrol Team BRM | Audi R8 LMS EVO ll | PA |
| 3 | 26 | J.Evans/E.Schutte | ARGT | Ferrari 296 GT3 | PA |
| 4 | 1 | B.Feeney/B.Schumacher | Kelso Electrical /Team MPC | Audi R8 LMS EVO ll | PA |
| 5 | 181 | W.Davison/R.Gracie | OnlyFans Racing | Ferrari 296 GT3 | PA |
| 6 | 88 | R.Wood/S.Brooks | Team BRM /Wolfbrook Motorsport | Audi R8 LMS EVO 11 | PA |
| 7 | 66 | J.Ojeda/P.Lucchitti | Move My Wheels by Tigani | Mercedes-AMG GT3 EVO | PA |
| 8 | 666 | G.Patterson/J.Drake | Team BRM | Audi R8 LMS EVO ll | PA |
| 9 | 56 | O.Targett/S.Smollen | Kollosche AMG by Tigani | Mercedes-AMG GT3 EVO | PA |
| 10 | 23 | J.Buchan/C.Campbell | Zagame Autosport | Ferrari 296 GT3 | PA |
| 11 | 2 | V.Astuti/D.Currie | Trading Garage /Team MPC | Audi R8 LMS EVO ll | PA |
| 12 | 24 | P.Stokell/M.Stoupas | KFC /Team MPC | Audi R8 LMS EVO 11 | T |
| 13 | 93 | T.D’Alberto/A.Deitz | Wall Racing | Lamborghini Huracan | PA |
| 14 | 71 | L.Youlden/N.Halstead | AED Consulting by Tigani | Porsche 911 GT3R | T |
| 15 | 14 | A.Gardner/W.Porter | Volante Rosso Motorsport | Aston Martin Vantage | T |
| 16 | 15 | J.Hunt/G.Emery | Volante Rosso Motorsport | McLaren 720s GT3 EVO | PA |
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