Envision Racing (2021–2023) Cassidy began competing in
Formula E for the
Envision Virgin Racing team starting with the
2020–21 season, partnering
Robin Frijns. Having failed to score during the first three races, Cassidy scored his first pole position during a wet-weather session at
Rome. However, Cassidy spun out of the lead on the opening lap as a result of a software glitch, before being pushed into the wall and out of the race by
Oliver Rowland. He scored points in the following rounds in
Valencia and
Monaco before achieving his maiden podium at the
Puebla ePrix. At the next race in
New York City Cassidy scored another pole and led the race until the closing laps, when a misjudged move by
Jean-Éric Vergne forced the Kiwi down to fourth. He returned to the podium on Sunday, though this would be his final podium of the year, as Cassidy finished a chaotic season of Formula E 15th in the standings, 23 points behind champion
Nyck de Vries. For the
2021–22 season, Cassidy remained at Envision, once again partnering Frijns. The opening half of his season yielded little success for the New Zealander, who only took three points finishes in the first ten races. Just like the previous year, Cassidy qualified on pole pole position for the first race in
New York, one he would convert into his first Formula E victory despite being involved in a multi-car pileup thanks to a sudden rain shower late in the race, as the event was aborted and countback rules were applied to the classification. He qualified on pole the following day only to be sent to the back of the grid as repairs to his car forced the team to use a fifth radiator of the season, earning Cassidy a 30-place grid penalty. Cassidy finished on the podium at
London as a result of a penalty for De Vries and ended the season eleventh in the standings, four positions behind teammate Frijns. Envision retained Cassidy ahead of the
2022–23 campaign, with him being partnered by
Season 2 champion
Sébastien Buemi. After two events that earned him points finishes, Cassidy scored back-to-back podiums at
Hyderabad and
Cape Town before missing out narrowly on victory to
Mitch Evans at the
São Paulo ePrix. The Kiwi continued his championship assault in Germany, winning the second race of the
Berlin ePrix, narrowing his gap to leader
Pascal Wehrlein to four points. At the next round in
Monaco, Cassidy charged from his starting spot of tenth to second within the opening seven laps, before executing a pass on title rival Evans to take victory in the principality. Cassidy struggled in
Jakarta, finishing seventh on Saturday before losing out on points on Sunday after damaging his front wing in a self-inflicted accident with Wehrlein, though he would return to form with a win at
Portland, having managed his car's energy well in a pandemonious,
peloton-style race.
Rome brought a podium on the opening day for Cassidy, however a crash caused by Evans on Sunday caused Cassidy to finish in a lowly 14th. Still with good chances to win the title, Cassidy qualified second for the first
London race but was promoted to pole after Evans's penalty for the Rome accident had been applied. During the race, drama ensued: Cassidy, who had been leading the race until his first attack mode activation dropped him back to fourth, became the victim in a teammate collision as miscommunication caused him to rip of his car's front wing, with Buemi, who had been ready to help Cassidy in his title ambitions by letting the Kiwi through, received no communication from his team. As Cassidy retired due to the damage,
Jake Dennis managed to take the title on Saturday. A win from pole on a rainy Sunday acted as consolation for Cassidy, who finished the season second in the championship.
Jaguar Racing (2024–2025) Cassidy switched to
Jaguar TCS Racing on a multi-year contract, replacing
Sam Bird and partnering fellow Kiwi driver
Mitch Evans for the
2023–24 Formula E season. Having been consistent through the first half of the season, Cassidy scored two victories and six more podiums. He entered the
2024 Portland ePrix with a lead of 25 points over
Pascal Wehrlein. Cassidy was leading race 1 of the Portland ePrix until the penultimate lap, where he spun out. He left Portland with no points scored across the two races. A disastrous qualifying in
London race 1 and an accident in race two with
António Félix da Costa meant Cassidy could only finish the season in third place. Cassidy left Jaguar following the end of the
2024–25 season.
Citroën (2025–) . In September 2025, Cassidy was announced to be joining new team
Citroën Racing for the
2025–26 season alongside double champion
Jean-Éric Vergne. == Endurance racing career ==