Oskar Weitzmann was the son of the photographer Jakob Weitzmann and Rosa, née Löwenthal. His five siblings, Berthold, Bronia, Josef, Osias and Willi Weitzmann, also worked in photography in Vienna. Oskar Weitzmann began a photography apprenticeship in 1914 in his father's studio. He served during the First World War in a flying squadron, in which he took aerial photographs. He completed his apprenticeship on 18 September 1919 and worked until 1923 as a commercial photographer at Gudrunstraße 126 in Vienna's 10th district and then, from 1926 to 1938, at Gumpendorferstraße 74 in the 6th district. He had a further photo studio with his brother Berthold at Pohlgasse 3 in the 12th district. Weitzmann published his photos in the 1930s in magazines such as Radio-Wien. In 1938 he was living with his wife Leontine (Leontyna), née Besen, and their two daughters Fritzi and Elsie (Ilse) at Haydngasse 10 in the 6th district. After the annexation, he and his family were persecuted by the Nazis on account of their Jewish origins. The studio in the 12th district was closed in April 1938 and the one at Gumpendorferstraße 74 was placed under the temporary administration of Gustav Nohynek in November of that year. The Gestapo seized the Weitzmann family's assets in the studio and apartment, and the Laconia-Institut was commissioned to liquidate the company. The photographer Wilhelmine Meytsky had originally applied to Aryanize the company, but it was Alfred Kral who was chosen, with the support of the Vienna Photographers' Guild in January 1939. The guild had commissioned the Viennese lawyer Josef Marian Strusewitz to carry out Aryanizations in the photography trade. Josef A. Detoni, an employee and secretary of the guild, functioned as treasurer. Both of the Weitzmann's studios in Vienna were deregistered on 31 December 1938 and deleted from the commercial register in January 1940 in accordance with the Gesetz zur Ausschaltung der Juden aus dem deutschen Wirtschaftsleben (Law on the Exclusion of Jews from German Economic Life). Oskar Weitzmann had fled with his family on 1 December 1938 (date of deregistration with the police) to Tirana in Albania, where he had a photo studio for a short time. When Albania was occupied by Italy in 1940, the family fled to the USA, and Weitzmann opened a studio in New York.
According to his asset declaration of 14 July 1938, Weitzmann had owned "a very large number of photographic plates". His wife Leontine Weitzmann, represented by Oskar Weitzmann' sister Bronia (Bronislava) Mate, applied in 1948 to the Landesgericht für Zivilrechtssachen (provincial court for civil law matters) in Vienna for restitution. The studio at Gumpendorferstraße 74 was restituted in 1951, after Alfred Kral died. The whereabouts of the photo archive are unknown.
From the project Durch das NS-Regime aus Österreich vertriebene und ermordete Fotografinnen und Fotografen und der Verbleib ihrer fotografischen Sammlungen (Subsidized by the National Fund of the Republic of Austria. Conducted by Walter Mentzel).