Oskar Michael Sima was born in Hohenau an der March, Austria on July 31st 1896. He studied acting in Vienna, and started out in theatres in Prague and Vienna. In 1924/25, he was featured in several plays at the "Theater in der Josefstadt", and in 1927 he relocated to Berlin, where he worked under legendary director Max Reinhardt and got prominent for mostly playing comic or satirical roles.

He made his debut as a screen actor in the 1921 production "Die Ehe der Hedda Olsen oder Die brennende Akrobatin". In the following decades, he became one of the most industrious supporting actors of German and Austrian cinema, appearing in over 250 films in 55 years. He was often cast as the petty bourgeois or choleric know-it-all, who looks for a bargain. He featured prominently in comedies like "Scampolo, ein Kind der Straße" (1932), "Ehestreik" (1935), "Fünf Millionen suchen einen Erben" (1938) and "Kohlhiesels Töchter" (1943); operettas like "Die Fledermaus" (1931) or "Gasparone" (1937) as well as melodramas like Kinderarzt Dr. Engel" (1936), "Frauenliebe-Frauenleid" (1937) and "Frau im Strom".

During that time, Sima voiced his support of the Nazi regime, explicitly welcoming Hitler's annexation of Austria. His opportunist stance was later criticized, but didn"t harm his career after WWII: Sima remained in high demand as an actor and appeared in many popular films of the 1950s and 1960s.

In 1967, a heart attack forced him to retire, and he retreated to his horse ranch near Vienna. In 1969, he was awarded a "Filmband in Gold" for his lifetime achievement in German cinema. Shortly afterwards, on June 24 1969, Oskar Sima passed away in his birthplace Hohenau.