Hirzegger began tobogganing on natural track at the age of five. He achieved his first international success at the European Junior Championships in Szczyrk in 1996 , when he won the bronze medal in the single seater. After several injuries at the beginning of his career, he made contact with the world's best in the late 1990s. In the 1997/1998 season , he achieved sixth place in the overall World Cup with equal points with his compatriot Robert Tomelitsch and a year later he was eighth overall. At the European Championships in Szczyrk in 1999 , he also finished eighth.
The then 23-year-old Styrian achieved his final breakthrough in the 1999/2000 season . Hirzegger won four of six World Cup races and took two fourth places, with which he was the overall World Cup winner ahead of his compatriot Gerhard Pilz and the Italian Anton Blasbichler . Thereupon he received the Golden Decoration of Honor for Services to the Republic of Austria . He achieved the worst result of the season at the 2000 World Cup in Olang . Here he only came in sixth. The 2000/2001 season started with two Hirzegger third and a second place, which he as World Cup leader and favorite for the World Cup in 2001 at his home track in Stein an der Enns traveled all. Hirzegger was six tenths of a second ahead after two of three races, but slowed down the third run and was overtaken by Anton Blasbichler by 19 hundredths of a second. Hirzegger won silver. In the team competition, which was held for the first time, he was also part of the Austria I team. However, the team did not make it into the ranking after the two-seater Beer / Kögl failed. The last two World Cup races of the winter (the fourth race of the season had to be canceled due to weather conditions) Hirzegger only finished in sixth and seventh position, which is why he dropped to third place in the overall World Cup after his half-time lead.
After a fourth place at the beginning of the 2001/2002 World Cup season, Hirzegger stood on the podium three times in a row and celebrated his fifth and final World Cup victory in the parallel competition in Triesenberg . With two sixth places at the end of the season, he finished second in the overall World Cup behind Gerhard Pilz, who celebrated three victories this season. At the European Championships in 2002 in Frantschach-Sankt Gertraud , he was seventh. In his last season, 2002/2003 , Hirzegger reached his final podium in third in the fifth World Cup race in Kindberg . In the end, he finished sixth in the overall ranking. At the 2003 World Championships in Železniki , Hirzegger, who had to wear a special splint after breaking his thumb, was twelfth.
After his active career, Hirzegger began working as a coach, including from 2005 for the Austrian women's team and since 2009 as the personal trainer of Gernot Schwab .