Ilott was introduced to motorsport at a friend's birthday karting party. He made his competitive karting debut in 2008 and quickly progressed, winning the WSK Masters Series and WSK Final Cup in 2012 and being named WSK Driver of the Year — the youngest ever recipient. In 2014, racing with Zanardi Strakka Racing, he claimed the CIK-FIA European Championship and WSK Super Masters Series titles.
Ilott stepped into single-seaters with the 2015 Toyota Racing Series before joining the FIA Formula 3 European Championship with Carlin aged sixteen, taking a podium at the Nürburgring in his debut season. He switched to Van Amersfoort Racing for 2016, taking his first single-seater win at Paul Ricard and a further victory at the Red Bull Ring. For 2017, he moved to Prema Powerteam, winning six races and finishing fourth in the championship, contributing to Prema's fifth consecutive Teams' title. He also competed in the GP3 Series in 2018 with ART Grand Prix, finishing third overall behind teammates Nikita Mazepin and Anthoine Hubert.
Ilott made his Formula 2 debut mid-season in 2017 at Silverstone with Trident. In 2019 he competed his first full F2 season, finishing eleventh with two podiums and a pole at Monza.
The 2020 season was his best in the formula. Driving for UNI-Virtuosi alongside Zhou Guanyu, Ilott claimed three wins, five pole positions, and six podiums. His first F2 victory came at the Red Bull Ring season opener. Despite a strong title challenge, he finished runner-up to fellow Ferrari Driver Academy member Mick Schumacher by a narrow margin.
After joining Red Bull's junior programme in 2015 and being released at year's end, Ilott signed with the Ferrari Driver Academy. He tested an Alfa Romeo C38 at Barcelona in 2019, completing 41 laps before a crash ended his running. He was named Ferrari's test driver for 2021 and served as Alfa Romeo's reserve driver, appearing in FP1 at the Portuguese and Austrian Grands Prix running the number 98. He was called back by Alfa Romeo for reserve duties at the 2022 Miami Grand Prix.
Ilott joined Juncos Hollinger Racing for the final three rounds of the 2021 IndyCar season, then raced full-time with the team through 2023. His best single-race result was fifth place, achieved at the 2023 Grand Prix of St. Petersburg and repeated at the Laguna Seca finale. He drove briefly for Arrow McLaren in 2024, deputising for injured David Malukas and finishing eleventh at the Indianapolis 500. He then joined Prema Racing for the full 2025 IndyCar season, recording back-to-back sixth-place finishes at Laguna Seca and Portland as the team's best results. Prema was subsequently omitted from the 2026 entry list due to financial difficulties.
Ilott made his 24 Hours of Le Mans debut in 2021 with Iron Lynx, co-driving a Ferrari 488 GTE to third place in the GTE Am class. In 2024 he joined Jota Sport in the FIA World Endurance Championship's Hypercar class. He took a feature race win at Spa-Francorchamps — Jota's first Hypercar victory — and the team claimed the FIA World Cup for privateers after finishing fifth at Fuji. From 2026 he competes in the IMSA SportsCar Championship with Wright Motorsports in a Porsche 911 GT3 R.
Ilott's career arc — from karting prodigy through the Ferrari junior ranks to multi-discipline professional — reflects the breadth of modern motorsport pathways. His near-miss at the 2020 F2 title remains the high-water mark of his single-seater years, while his WEC Hypercar victory at Spa marked a new chapter in endurance racing.