In the state series, he won eight out of 12 races, including seven in a row, while he scored two wins, two runner-up finishes, and a pole position in the national division.

Brabham won the title over his teammate Spencer Pigot by seven points, capturing four wins from 11 podium finishes in the fourteen race season.

Brabham attributed his lower points finish than hoped to his lack of experience, having progressed through three levels of the Road to Indy in as many years, and his difficulties in adjusting to the series' use of Cooper Tires after mainly racing with Firestone.

[7] In October 2021, Brabham rejoined Andretti's Indy Lights programme for the Chris Griffis Memorial Test at Indianapolis, during which he set the tenth-best time.

[8] Three months later, he formally committed to the 2022 Indy Lights season with the team;[9] at 28 years of age, he was the oldest driver in the field.

[10] He won the season opener at St. Petersburg after passing teammate Christian Rasmussen, who ran out of fuel, on the penultimate lap.

His first win of the season came at Adelaide Street Circuit's third race, where he capitalised on Robby Gordon entering the final corner too wide on the last lap.

[30] Further triumphs came at Long Beach, Barbagallo Raceway,[31] Texas Motor Speedway,[32] Road America,[33] and Sydney Motorsport Park.

[34] Brabham battled with Gavin Harlien for the championship throughout the season,[35] and a victory at the season-ending 2019 Race of Champions clinched him the 2018 title.

[37] Brabham opened the 2019 season by winning the second race of the Circuit of the Americas weekend despite suffering from a foodborne illness the previous night.

[50] Although Brabham did not commit to a full 2022 season due to Indy Lights, he continued to make occasional starts as SST's prize money structure provides him with a sustainable salary.

[51] In 2017, Brabham returned to Australia to race in the Supercars Championship, making his debut at the 2017 Perth SuperSprint for Lucas Dumbrell Motorsport in place of Taz Douglas.

[53] In 2017, Brabham, Bill Hynes and Alexandre Prémat competed in the Utah Motorsports Campus 6 Hour Enduro, where they won EXR Racing Series class and finished tenth overall.

[56] Later in the year, he entered the Pirelli World Challenge's GT class, driving for CRP Racing at Portland International Raceway.

20 Ford Mustang, he caught and passed 7-time series champion Ernie Francis Jr. in the final 50 feet of the last lap for the win.

[58] Brabham's family is heavily involved in motorsports, with father Geoff being a former CART driver while mother Roseina is a jet ski champion.