Bradl made his first 125cc World Championship appearances as a wildcard in 2005 and 2006, competing on a KTM alongside his participation in the German domestic series. A serious injury during practice for the 2006 Malaysian Grand Prix — when he was struck by another rider — interrupted his development but did not derail his career. He moved to the Spanish domestic championship with Blusens Aprilia and won the 125cc Spanish title, beating teammate Scott Redding by just five points. He also received an offer from Alberto Puig to join the Repsol Honda 250cc factory team for 2007, which he ultimately declined.
For the 2008 season, Bradl joined Grizzly Gas Kiefer Racing on an official factory Aprilia RSA 125. He claimed his first Grand Prix victory at Brno — a track where his father had also won in 1991.
Bradl moved to the Moto2 class for 2010, finishing ninth in his debut season with one win at Estoril. The 2011 season was transformative. He won four of the first six races and built a substantial championship lead over Marc Marquez. The title battle remained close until Marquez suffered a heavy crash during free practice at the Malaysian Grand Prix, sustaining eyesight problems that ruled him out for the remainder of the season. Bradl was crowned Moto2 World Champion at the final round in Valencia.
Bradl joined the LCR Honda satellite team for his MotoGP debut in 2012. He ran consistently inside the top ten throughout the season, with a best result of fourth at the Italian Grand Prix, and claimed the Rookie of the Year award while finishing eighth overall.
In 2013, Bradl's season highlight came at Laguna Seca in the United States Grand Prix. He took pole position and finished second in the race behind Marc Marquez, with Valentino Rossi behind him — his first and best MotoGP podium. He closed the year seventh in the championship with 156 points, but a crash at the Malaysian Grand Prix that broke his ankle disrupted what might have been a stronger finish.
He remained with LCR Honda for 2014 before losing his seat to Cal Crutchlow, who joined with factory-specification machinery.
Bradl moved to Forward Racing for 2015 on a Yamaha Forward open-specification machine, partnering Loris Baz. The season was difficult, with limited points haul and personal injury again interrupting his campaign. Following the arrest of team boss Giovanni Cuzari mid-season, Bradl moved to Aprilia Gresini Racing for the second half of 2015. He remained with the team through 2016, partnering Alvaro Bautista, collecting 63 points and finishing 16th overall.
Bradl spent one season in the Superbike World Championship with the Red Bull Honda Team, competing in six full rounds and four partial rounds, finishing 14th in the standings.
From 2018 onwards, Bradl joined Honda Racing Corporation as an official test rider. In this role he made multiple return appearances to MotoGP as a replacement for injured factory riders, most extensively deputising for Marc Marquez during Marquez's long injury absences. Bradl replaced Marquez from the Czech Republic round of 2020 onwards after the Spaniard was seriously injured at the Spanish Grand Prix in August. He made further wildcard and replacement appearances through the 2021 and 2022 seasons.
Bradl's career trajectory — world champion at intermediate level but unable to break through as a consistent top-five MotoGP finisher — reflects the challenge the satellite-team era posed for riders without full factory support. His Laguna Seca pole and podium in 2013 remain the clearest evidence of his peak capability. As an HRC test rider, he has played a significant role in Honda's ongoing development programme during one of the marque's most challenging competitive periods. His family ties to the sport, through father Helmut Bradl, add a generational dimension to his story.