Healy grew up in Wordsley, in the Black Country, and qualified for Ireland through his grandparents, pledging his allegiance as a teenager rather than carrying on with Great Britain. His father had raced and brought him into the sport without pushing him at it. At the 2019 Tour de l'Avenir he rode clear of Morten Hulgaard and Matteo Jorgenson with four kilometres left and won stage five.
He won the Irish national road race in 2020 and the national time trial in 2022, then took the road title again in 2023. That same spring came the results that carried his name past Ireland. He was second at Brabantse Pijl, a single second behind Dorian Godon, and second again at the Amstel Gold Race, thirty-eight seconds down on Tadej Pogačar. A month later he won stage eight of the Giro d'Italia, from Terni to Fossombrone.
He rode the 2024 Tour de France in the day's breakaways rather than for a place on general classification and came out of it 27th. He goes up the road early, alone or with two or three others, and holds a heavy gear on the hilly, unsettled terrain that suits neither the pure climbers nor the fast men. It is a way of racing that loses far more often than it wins.
In 2025 he was third at Liège–Bastogne–Liège, caught in the group sprint for second behind Giulio Ciccone while Pogačar rode away alone. At the Tour de France that July he attacked on stage six to Vire Normandie and won by himself, then rode into the yellow jersey on stage ten at Puy de Sancy. He held it for two days, finished ninth overall in Paris and was named the race's most combative rider.
At the world championships in Kigali that September he was third again, behind Pogačar and Remco Evenepoel.









