Joan Mir was born in Palma and prior to his premier class career he competed in the Red Bull MotoGP Rookies Cup in 2013 and 2014. He also contested in the CEV Moto3 Junior World Championship in 2015 and finished fourth overall. Mir made his full-time debut in Moto3 in 2016, racing for Leopard Racing alongside Fabio Quartararo and Andrea Locatelli. Mir achieved his first victory at the Austrian Grand Prix and went on to score a further 2 podiums that year to finish in 5th overall. The Spaniard remained with Leopard for the 2017 season, and he dominated the class with 10 wins and 13 podiums to go on and win the championship. 

In 2018 Mir moved up to Moto2 with Marc VDS for a three-year contract with the team. He finished the season in 6th place overall with four podiums and the rookie of the year award. Midway through the 2018 season, it was announced that Mir would end his contract with Marc VDS prematurely and make the move up to MotoGP with the Suzuki Factory Team for the 2019 season. He achieved consistent top-10 finishes in his rookie MotoGP season and finished as second-best rookie behind former teammate, Fabio Quartararo. Mir proved his consistency in the 2020 season as he became a regular podium finisher and a consistent points finisher. He became a championship contender and thanks to some inconsistent finishes from his title rivals, he was leading the championship despite not winning a race. Mir eventually took his maiden win at the penultimate round of the season and went on to win the championship a week later in Valencia. For the 2021 season Mir scored 6 podiums and had a number of consistent top-10 finishes to eventually finish 3rd overall in the championship. 2022 was a tough season for Mir, he started off with some consistent points finishes but suffered some bad luck with a handful of retirements and then an injury which put him out for a couple of races. It was also announced mid-way through the season that the Factory Suzuki would withdraw from the series with 2022 being their last season. This meant for the 2023 and 2024 seasons Mir signed a new contract with the Repsol Honda Team.