From 1927 until 1930 he attended the arts and crafts school in Graz and studied under Adametz. From 1932 until 1940 he studied at the Academy of Fine Arts, Vienna under Anton Hanak and Viktor Müllner. He soon withdrew from the influence of his teachers looking for new role models. From 1946 until 1948 he worked freelance at the master school under Fritz Wotruba (cubistic-constructivist design principles) who just after the war had ended had come back to Vienna. Until 1952 Leinfellner was Wotruba’s assistant. His first works would consist of experiences he gained in the war. Like in Wotruba, also in Leinfellner there is no imitation of figurative events, but rather a new determination of sculptural practice in post-war years.
Leinfellner’s flat and studio were meeting points for Vienna’s intellectuals in the 1940s and fifties. In 1947 he co-founded Artclub Vienna. In 1950 he received the prize of the city of Vienna for Fine Arts. In 1956 he participated in the Vienna Biennial. From 1959 until 1972 the artist taught at the University for Applied Arts, Vienna, where he was in charge of a master class for ceramic sculpture. In 1959 he took part in documenta2 in Kassel. In 1969 in the context of steirischer herbst he participated in trigon´69 at Schloss Eggenberg. In 2002 his works were shown at Albertina in Vienna.
Whilst his early works served in coming to terms with what he had experienced (Bombenruinentorso (bomb ruins torso), 1946), over the years he would find a sovereign and calm language of forms, shown for instance in his ‘contemplating’ female figures of the early 1950s. Influenced by Henry Moore, he occupies himself with the human figure in the three basic positions: to stand, to sit, to lie. He was also interested in primitive art, which later became visible in his sculptures. His large dormant female bodies with their strange proportions reminiscent of Matisse’s sculptures became very well known. In the course of his oeuvre, his dormants received stylistic variations. Leinfellner worked with marble as well as with artificial stone, clay, lead or bronze. Finally he also discovered ceramics for himself and in his teaching specialised in it.
Also the list of his commissioned works in the public field is impressive. Both inlay works at the foyer of Vienna State Opera or the relief masks at the smoker’s foyer at the Großes Festspielhaus theatre in Salzburg are by him.