Mona grew up in Helsingborg and studied at the Dramatens elevskola (Royal Dramatic Theater Academy). She made her first film appearance in Anderssonskans Kalle på nya upptåg (Kalle Anderssonskan's New Pranks, 1923) directed by Sigurd Wallén. That same year, Mona and her classmate Greta Gustafson (who would change her name to Greta Garbo that same year) were selected by the school to audition for noted Swedish film director Mauritz Stiller. Both actresses were cast in his upcoming film, the epic romance Gösta Berlings saga (The Saga of Gosta Berling) in 1924. The film was based on the 1892 debut novel by Selma Lagerlöf and featured Lars Hanson as the handsome young priest, Gösta Berling, who is fired over his drinking and improper lifestyle. Shamed, he is later hired by an unscrupulous and wealthy woman to be a tutor to her beautiful step-daughter played by Mona Mårtenson.
