Juncadella comes from a notable Spanish motorsport lineage. He is the son of Xavier Juncadella and the nephew of José María Juncadella, Alex Soler-Roig, and Luis Pérez-Sala, all racing drivers. Pérez-Sala drove for the Minardi Formula One team in 1988 and 1989 and later served as team principal of the Spanish HRT F1 outfit in 2012.
Juncadella began karting in 2004 before moving into formula racing via the 2007 Master Junior Formula season, finishing runner-up with seven wins. He then raced in Formula BMW ADAC at the end of 2007, graduating to the full Formula BMW Europe series with EuroInternational in 2008. He took two wins at the Hungaroring and finished fourth in the standings, then improved to runner-up in 2009 — including one win at Monza — behind Brazilian team-mate Felipe Nasr.
The step up to Formula 3 Euro Series came for 2010 with Prema Powerteam, backed by the Astana cycling team. Juncadella claimed his first pole at Circuit Paul Ricard in his very first event. His Formula 3 career culminated in the championship title and a victory at the Macau Grand Prix, establishing him as one of Europe's most promising young single-seater talents.
Juncadella tested with Williams F1 at the Young Drivers test at Silverstone. On 24 January 2014 he joined Force India as a reserve driver, attending all races and participating in Friday practice sessions. In December 2024 he returned to the team's successor, Aston Martin, as a simulation driver for the 2025 season.
Juncadella entered the Deutsche Tourenwagen Masters in 2013 with Mercedes, spending three seasons with Mücke Motorsport before a year away to focus on Blancpain GT competition. He returned to DTM in 2018 and delivered his strongest single-seater-adjacent campaign, scoring three pole positions, two podiums, and a race victory at Brands Hatch on the way to fifteenth in the standings. The 2019 season saw him join the Aston Martin Vantage project with R-Motorsport, where he led the team's results ahead of teammates Paul di Resta, Jake Dennis, and Ferdinand Habsburg, ultimately finishing fourteenth in points.
Juncadella returned to the DTM again in 2021 for the series' first season under GT3 regulations, driving for GruppeM Racing's Mercedes. He collected points regularly and took a podium at the Nürburgring, finishing ninth in the standings.
After several partial Blancpain seasons, Juncadella contested the full GT World Challenge Europe Endurance Cup in 2022 with AKKodis ASP alongside fellow Mercedes factory drivers Raffaele Marciello and Jules Gounon. The trio won the 24 Hours of Spa and sealed the Endurance Cup title with another victory at the Barcelona season finale.
Simultaneously, Juncadella competed across all four rounds of the 2022 Intercontinental GT Challenge, adding wins at Indianapolis and Spa and a runner-up result at the Bathurst 12 Hours to claim the IGTC drivers' championship — the most global of the GT world titles.
In 2023, Juncadella joined WeatherTech Racing in the GTD Pro category of the IMSA SportsCar Championship, pairing with Jules Gounon for sprint events and adding Maro Engel for endurance races. The trio won their class at the 24 Hours of Daytona and the Petit Le Mans season finale, securing the Michelin Endurance Cup title. Two additional sprint wins placed the entry second in the overall GTD Pro classification.
Juncadella's career arc — from Formula 3 champion and F1 test driver to GT endurance title holder — is unusual in contemporary motorsport and reflects his adaptability across disciplines. His 2022 season in particular, which combined the Blancpain Endurance Cup and Intercontinental GT Challenge crowns, stands as the peak of his career in world-level GT competition.