Mario König was educated at the University of Graz 1991–1997, Mag. iur. 1997, Dr. iur. 2004; Fordham Law School, New York 1998–1999, Master of Laws (LLM) 1999.

He took the New York Bar examination in 1999, the Austrian Bar examination in 2002 and the Liechtenstein Bar examination in 2007. He was admitted to the New York Bar in 2001 and to the Liechtenstein Bar in 2009.

He practised as a judicial clerk at the Provincial Court of Appeal, Graz, 1997–1998 and 1999; he was a trainee attorney in Vienna 2000–2004; and has been a member of the Chartered Institute of Arbitrators (MCIArb) since 2003. He was an associate at Marxer & Partner from 2004; and has been a partner since 2009.