As a result of finishing championship runner-up in the 2008 Formula Master season, in November of that year, Leimer took part in a prize GP2 test with Italian team Trident Racing at the Paul Ricard circuit in France, and a year later he tested with the DAMS team at the same venue as a prize for winning the Formula Master title.

In October 2009, Leimer tested with Tiago Monteiro's Ocean Racing Technology team at Jerez and later that month he was confirmed as a driver for the team in the 2009–10 GP2 Asia Series season, racing alongside fellow Formula Master graduate Alexander Rossi, and former British Formula 3 driver Max Chilton.
Leimer continued with the team into the 2010 GP2 Series, and was partnered by Chilton.
At the first round of the season in Barcelona, Leimer finished eighth in the feature race, a result which gave him pole position for the reverse grid sprint event which he won from the Rapax Team entry of Luiz Razia.
However, he did not score any further points, limiting himself to nineteenth place in the drivers' championship.

For 2011, Leimer moved to the Rapax team alongside Julián Leal.
He finished fifth overall in the Asia series, and then proceeded to take his second category win in the main series.
As was the case the previous year, the victory came in the sprint race at the Catalunya circuit, and he again set the fastest lap in the process, although on this occasion he owed his reverse-grid pole position to Romain Grosjean's disqualification from the feature race.
Another haul of points at Monza saw him improve to 14th position in the championship standings.
He also won the feature race of the non-championship event held at the Yas Marina Circuit.
Leimer switched to the Racing Engineering team for 2012, where he partnered Nathanaël Berthon.
Despite failing to win a race during the season, his improved consistency, consisting of six podium finishes, saw him improve to seventh place in the drivers' championship.
Leimer took the GP2 driver's championship title in 2013, with seven podium finishes and three wins.
As a result of finishing championship runner-up in the 2008 Formula Master season, in November of that year, Leimer took part in a prize GP2 test with Italian team Trident Racing at the Paul Ricard circuit in France, and a year later he tested with the DAMS team at the same venue as a prize for winning the Formula Master title.
In October 2009, Leimer tested with Tiago Monteiro's Ocean Racing Technology team at Jerez and later that month he was confirmed as a driver for the team in the 2009–10 GP2 Asia Series season, racing alongside fellow Formula Master graduate Alexander Rossi, and former British Formula 3 driver Max Chilton. Leimer continued with the team into the 2010 GP2 Series, and was partnered by Chilton. At the first round of the season in Barcelona, Leimer finished eighth in the feature race, a result which gave him pole position for the reverse grid sprint event which he won from the Rapax Team entry of Luiz Razia. However, he did not score any further points, limiting himself to nineteenth place in the drivers' championship.
For 2011, Leimer moved to the Rapax team alongside Julián Leal. He finished fifth overall in the Asia series, and then proceeded to take his second category win in the main series. As was the case the previous year, the victory came in the sprint race at the Catalunya circuit, and he again set the fastest lap in the process, although on this occasion he owed his reverse-grid pole position to Romain Grosjean's disqualification from the feature race. Another haul of points at Monza saw him improve to 14th position in the championship standings. He also won the feature race of the non-championship event held at the Yas Marina Circuit. Leimer switched to the Racing Engineering team for 2012, where he partnered Nathanaël Berthon. Despite failing to win a race during the season, his improved consistency, consisting of six podium finishes, saw him improve to seventh place in the drivers' championship. Leimer took the GP2 driver's championship title in 2013, with seven podium finishes and three wins.
Fabio Leimer