Raised by a particularly devout uncle and aunt, Oswald Tschirtner expressed his desire to become a priest at a very young age and was placed in a seminary at the age of ten. In 1939, he was drafted into the German army and participated in the Battle of Stalingrad, where he served as a radio operator. Towards the end of the war, he was taken prisoner and interned in a camp in southern France. Released in 1946, he began experiencing psychotic episodes. Diagnosed with schizophrenia, he was hospitalized several times. In 1954, he was admitted to the Maria Gugging Psychiatric Hospital in Klosterneuburg, near Vienna, where he remained for the rest of his life. It was there, encouraged by Dr. Leo Navratil, that he began drawing in the 1960s. In 1981, he joined the Gugging artists' residence.

His minimalist drawings, bordering on abstraction, are executed in India ink on paper, most often in small format. They mostly depict the silhouettes of androgynous figures consisting of two arms and a pair of legs directly attached to a head. The torso and the extremities of the limbs are systematically omitted. When Tschirtner does not depict figures, the forms are even more austere; a landscape might consist of a single line, an animal a single dot. Some drawings, especially from his later years, are highlighted with one color, rarely two. He signs his works O.T.