Oskar Keymer was born in 2003. He made his screen debut in a small role in the refugee drama "Westen" ("West", 2013). The following year, he appeared in two episodes of the TV series "Heldt". Next came his first leading role in the comedy "Hilfe, ich hab meine Lehrerin geschrumpft" ("Help, I Shrunk My Teacher"), in which he plays a school boy who has to team up with his magically shrunken principal.

Keymer went on to star in "Weisse Steine", a one-hour student film, and the theatrical release "Conni & Co." (2016), which is based on the popular books of the same name.