In 2018, Alonso raced in the 24 Hours of Daytona for the first time. He shared the 22 United Autosports Ligier JS P2 with Lando Norris and Philip Hanson, which finished 38th overall after mechanical issues affected his race. He later raced the full 2018–19 FIA World Endurance Championship alongside Sébastien Buemi and Kazuki Nakajima at Toyota Gazoo Racing. Sharing the No. 8 Toyota TS050 Hybrid, the trio won the World Drivers' Championship after a season-long duel with their teammates Mike Conway, Kamui Kobayashi and José María López with five race victories, including the 24 Hours of Le Mans in both and . Alonso returned to compete in the 24 Hours of Daytona in 2019. He won the rain-shortened race in a Wayne Taylor Racing-entered Cadillac DPi-V.R with Kobayashi, Renger van der Zande and Jordan Taylor.