Masià competed in the FIM CEV Moto3 Junior World Championships between 2015 and 2017, finishing second overall in his final season behind Dennis Foggia. He also participated in the 2014 Red Bull Rookies Cup.
Masià made his Moto3 World Championship debut in 2017 as a replacement for the injured Darryn Binder. He immediately impressed by setting the fastest lap in his debut race. Strong performances secured him a full-time ride for 2018 and 2019. In 2019 he recorded his first Moto3 pole position and took his maiden Grand Prix victory at the second round of the season in Argentina.
For 2020 Masià joined Leopard Racing, a step considered a promotion given the team's championship-winning pedigree. He won two races, took three podiums, and finished sixth in the championship with 140 points.
Two seasons with the established Red Bull KTM Ajo team produced three more victories and multiple podiums. His best championship position came in 2021 when he finished fourth in the standings, suggesting he was among the class's top contenders.
Masià returned to Leopard Racing for 2023 and delivered his finest season. He won three races, took ten podiums, and secured six pole positions — his most productive statistical campaign since entering the class. He clinched the Moto3 World Championship with a race to spare at the Qatar Grand Prix, sealing the title with a victory that also proved to be his final race win and podium of the year. It was a dominant, consistent campaign that justified his status as one of the small-class's most experienced and polished competitors.
After his Moto3 championship, Masià moved to Moto2 with the Pertamina Mandalika SAG Team for 2024. The season did not unfold as hoped: mid-year the team underwent a change of name and ownership, becoming the Preicanos Racing Team, and stability was hard to find. His best result across the year was a thirteenth place at the Catalan Grand Prix.
For 2025 Masià had signed with Preicanos Racing Team again, but the team collapsed without clarity before the season started, leaving him without a ride. No other Moto2 team had seats available. Being without a contract just one year after winning the Moto3 World Championship was an unusually harsh outcome for a reigning champion.
Without a Moto2 option available, Masià joined the Orelac Racing Verdnatura team to compete in the Supersport World Championship on a Ducati Panigale V2. He adapted quickly: he won at the fifth round of the season in Most, Czech Republic, and finished the year third in the standings — the best-placed Ducati rider and the top rookie in the class. He won again at the final round of the season.
He renewed with the team for 2026 and by mid-season was placed third in the standings with three victories and several further podiums, demonstrating that the transition to Supersport machinery had suited him well.
Masià's Moto3 championship capped the career of one of the class's most persistent competitors: he spent seven seasons in the small class and graduated through multiple respected teams before winning the title. The corner named at Ricardo Tormo is a rare formal geographic honour for a motorcycle racer. His post-championship experience highlighted an ongoing structural issue within the Grand Prix ladder — a Moto3 champion finding no Moto2 team available — while his rapid success in Supersport suggested he remained a high-calibre talent fully capable of winning at international level in a new category.