Mario Haas was active in SK Sturm Graz's youth section for ten years before playing his first game for the club's professionals in the spring of 1993.

From the spring of 2007, Mario Haas played again for his regular club Sturm Graz, with whom he triumphed in the Austrian Cup for the fourth time in 2010.

He was substituted in the match against Kapfenberger SV on February 12, 2011, marking his 412th appearance for SK Sturm Graz in the Bundesliga and making him the team's sole record holder ahead of Günther Neukirchner.

[4] At the general assembly of SK Sturm Graz on January 18, 2016, he was honored as honorary captain together with Günther Neukirchner and Andy Pichler.

[5] Haas made his debut for the Austria national team in an April 1998 friendly match against the United States and was a participant at the 1998 FIFA World Cup.