Juncadella made his competitive car racing debut in 2007 following to a relatively short career in karting. He competed part-time in the 2007 Formula BMW ADAC and went on to score second place in the Master Junior Formula. In 2008, he was fourth in the Formula BMW World Final, as a Red Bull Junior driver, and was second in the 2009 Formula BMW Europe championship. He joined PREMA for his move to Formula 3 in 2010, and was third in the F3 Euro Series in 2011. That year, he handed the the team its first win in the mighty Macau Grand Prix. In 2012, Juncadella won the F3 Euro Series and European Championship combo, moving to DTM and F1 testing duties. In 2016, he made the switch to GT racing and was selected as a Mercedes-Benz manufacturer driver, a role he still covers today.