Holzer began his motorsport career in karting in 1997, which he held until 2003. 2004 joined the young gun in the German Formula BMW so into formula racing. Starting for AM Holzer Rennsport, he was 20th in the overall standings. In 2005, he played his second season in the German Formula BMW and qualified with the 13th overall for the Formula BMW World Final, which he won from pole position before starting Sébastien Buemi and Nico Hulkenberg. 2006 Holzer joined again in the German Formula BMW and won three races. At the end of the season, he finished behind champion Christian Vietoris and Mika Mäki third place in the overall standings.
2007 remained at Holzer AM- Holzer Rennsport and moved to the Formula 3 Euro Series. His best finish was seventh place. He could not retract points and finished the season 19th overall. 2008 Holzer returned to the Formula racing back and moved to the GT racing. He started in the Porsche Carrera Cup Germany for the UPS Porsche Junior team and was fifth with a race win. He also drove in six rounds of the Porsche Supercup. With the premature end of the junior program Holzer in 2009 received a cockpit in Prospeed Competition in the FIA GT Championship. He started in a Porsche 997 GT3 RSR in the GT2 class and was with a class win at the last race of eight in this category. As a junior, he started for Porsche works driver also in selected championship events of different GT series. Among other things, the Asian Le Mans Series, where he finished on the podium in the GT2 class.
2010 won the German, the 24 -hour race in Dubai for IMSA Performance Matmut, along with Porsche works driver Patrick Pilet and team boss Raymond Narac. For more Holzer season but returned again to Prospeed Competition back to start now in the Le Mans Series.
Holzer has already had experience in a Formula 1 car, as he as a reward for winning the Formula BMW World Final graduated Formula 1 test driving for BMW Sauber in 2006.