Johannes Nussbaum already acted in the school theater at Mödling elementary school. At the suggestion of the theater group supervisor, Nussbaum applied to the Viennese agency Eva Roth Casting, a well-known agency for casting children and amateur actors. He successfully completed an audition and audition for the film Import Export by Ulrich Seidl, shot in 2005/2006 and completed in May 2007, in which he made his film debut at the age of nine, alongside Maria Hofstätter and Petra Morzé. He was selected from among several hundred children for his first film role.

1990