Feeney grew up on the Gold Coast and began competitive karting at eleven years of age, winning multiple Queensland state championships and claiming the Australian KA2 Championship in 2017. In 2018 he moved into circuit racing via the Toyota 86 Racing Series, becoming the youngest race winner in that series' history at fifteen.
In 2019 Feeney joined Paul Morris Motorsport for the Super3 Series, winning the championship as a rookie — again the youngest champion in that competition's history. He totalled twelve podiums across fifteen races and defeated championship rival Jayden Ojeda by 24 points. Tickford Racing then signed him for the 2020 Super2 Series, but after a difficult debut season he transferred to Triple Eight Race Engineering for 2021. Driving the iconic No. 888 VF Commodore, Feeney won five races and secured the Super2 title by a 177-point margin over Zak Best, becoming the youngest driver to win that championship at nineteen years old. The title earned him the Motorsport Australia Young Driver of the Year award.
Feeney's main-series debut came at the 2020 Bathurst 1000, where he co-drove with James Courtney for Tickford Racing, finishing tenth on his eighteenth birthday — one of the youngest starters in championship history.
Following Jamie Whincup's retirement from full-time competition after the 2021 season, Feeney was named as his successor at Triple Eight, inheriting the famous No. 88 entry. A wildcard appearance at the 2021 Bathurst 1000 alongside Russell Ingall ended with a crash on lap 143 after a strong early showing.
In his first full Supercars season Feeney scored points in 23 of 24 races. His maiden championship podium came at the Tasmania SuperSprint, and he claimed his first win at the 2022 Adelaide 500 — holding off Chaz Mostert to become the last driver to win a Supercars race in a Holden after the manufacturer's departure from the sport.
The introduction of Gen3 machinery in 2023 suited Feeney well. He won five races through the season, including a Sandown 500 victory partnered with Whincup, and ended the year third in the standings behind Brodie Kostecki and Shane van Gisbergen.
When van Gisbergen departed for NASCAR, Will Brown joined Triple Eight as Feeney's teammate. The pair dominated the season, but despite winning more races than Brown — including a victory at the Bathurst 500 — Feeney's consistency fell short of his teammate's and he finished runner-up in the championship.
The 2025 Supercars season introduced a restructured format split across three cups: the Sprint Cup, Enduro Cup, and Finals Series. Feeney dominated the Sprint Cup segment, winning twelve of the eight rounds' races and claiming thirteen pole positions, including a five-race winning streak. He clinched the inaugural Sprint Cup title at Ipswich with a 345-point advantage over second-place Matt Payne. Mid-season, Triple Eight announced he had been re-signed alongside Brown through to the end of 2029.
The Enduro Cup yielded more modest results, but Feeney entered the Finals Series in contention for the overall championship. A controversial spin inflicted by Ryan Wood in the Adelaide Grand Final's final race — dropping him from second to twentieth — ultimately relegated him to third in the season standings behind Chaz Mostert and Brown. During the campaign he broke Scott McLaughlin's single-season pole record, setting nineteen poles over the year.
Beyond Supercars, Feeney has competed in sportscar racing. In 2020 he stood in for Jake Camilleri at MARC Cars Australia for the Bathurst 12 Hour, finishing fifteenth outright and winning the class. He won the GT World Challenge Australia Pro-Am category in 2025 alongside Brad Schumacher, and made an IMSA SportsCar Championship appearance at Indianapolis driving a Mercedes-AMG GT3 in the GTD Pro class. He also made an open-wheel outing in the 2025 Formula Regional Oceania Championship, taking pole position in the third race.
At an age when most drivers are still proving themselves in junior categories, Feeney has accumulated 24 Supercars race wins and holds records for the youngest Super3 and Super2 champions. His back-to-back title fights at Triple Eight, combined with the Sprint Cup championship, establish him as one of the leading contenders for future Supercars titles alongside his teammate Will Brown.