Atlanta-based international auto parts conglomerate Genuine Parts Company, through its consumer brand Repco, replaced Virgin Australia as the series' naming rights sponsor under an initial five-year partnership later extended to eight years. A new five-year broadcast deal also commenced in 2021, with Fox Sports retaining full-round coverage while the Seven Network took over from Network Ten as the free-to-air broadcaster, showing six rounds live including the Bathurst 1000.
The off-season brought sweeping structural changes. General Motors' February 2020 announcement that it would retire the Holden name by end of 2020 meant Commodore ZB cars entered 2021 without factory support. Team Penske sold its majority stake in DJR Team Penske, which reverted to the Dick Johnson Racing name last used in 2014. Dick Johnson Racing fielded an entirely new driver lineup: Anton de Pasquale, who moved from Erebus Motorsport, was joined by Will Davison, returning to the team he had last driven for full-time between 2006 and 2008.
Reigning three-time champion Scott McLaughlin did not defend his title, departing to race in the IndyCar Series with Team Penske — the first time a defending champion had not returned since Craig Lowndes chose not to defend his 1996 title. Fabian Coulthard moved to Team Sydney.
Erebus Motorsport introduced a wholly new roster, replacing the departing David Reynolds and Anton de Pasquale with Super2 graduates Will Brown and Brodie Kostecki. Reynolds returned to Kelly Grove Racing — a team restructured after the Grove Group purchased a majority stake in Kelly Racing — having last raced for the outfit in 2011. Rick Kelly retired from full-time racing at the end of 2020.
Tickford Racing scaled back from four cars to three, with Lee Holdsworth departing and Jack Le Brocq moving to the number 5 car. Blanchard Racing Team separated from Brad Jones Racing and formed a standalone operation with an ex-23Red Racing Ford Mustang, prompting Brad Jones Racing to purchase 23Red Racing's Racing Entitlement Contract that had been leased to Tickford in 2020.
The season opened at Mount Panorama with the Mount Panorama 500 sprint round, filling a gap created when the Bathurst 12 Hour was cancelled due to travel restrictions. The Adelaide 500 did not appear on the calendar for the first time since 1998, as the South Australian Tourism Commission withdrew financial support citing pandemic-related factors and dwindling attendances. Multiple further rounds were disrupted or cancelled as COVID-19 Delta outbreaks spread through New South Wales and Victoria. Events in Perth, Auckland, Phillip Island, Winton, and the Gold Coast were abandoned; the series pivoted to a quadruple-header at Sydney Motorsport Park using a mix of formats and day-night sessions before closing with the Bathurst 1000.
A pre-season test was split between Queensland Raceway for Queensland-based teams and Team Sydney, and Winton for Victorian teams and Brad Jones Racing, due to border closures.
Five bonus championship points were introduced for the driver setting the fastest lap in sprint races, conditional on completing at least 75 percent of the race distance. A third tyre compound, the Super Soft, was trialled at Darwin and the fourth Sydney Motorsport Park event. The Bathurst 1000 used a dedicated points scale, while sprint events and the 2x250 km formats at Mount Panorama and Townsville each used their own systems.
Kelly Grove Racing driver David Reynolds was stood down from the final Sydney Motorsport Park rounds in November after failing to comply with New South Wales Health Orders regarding mandatory COVID-19 vaccination. Luke Youlden replaced him, making his solo series debut. Reynolds was originally expected to return for the Bathurst 1000, and an announcement on 18 November confirmed he would rejoin the team for round 11 at Sydney Motorsport Park.
Two wildcard entries appeared at The Bend, Darwin, and round 9 at Sydney Motorsport Park: Thomas Randle drove a fourth car for Tickford Racing and Kurt Kostecki competed for Walkinshaw Andretti United. Triple Eight Race Engineering entered a third car at the Bathurst 1000 for Russell Ingall and Broc Feeney.
The 2021 season marked Shane van Gisbergen's second drivers' championship, secured amid one of the most disrupted Australian motorsport calendars on record. The transition away from Holden as a factory-backed marque, the exit of long-serving drivers including Rick Kelly, and the debut of a new generation of Super2 graduates reshaped the competitive landscape of the championship heading into the mid-decade era.