In 1924, Uiberreither joined the Schill Youth (Schilljugend). He studied law and worked as a construction aid worker. In 1930 he became a secretary for the Workers' Sickness Fund (Arbeiterkrankenkasse) in Graz. In 1931, he joined the SA, and in 1933 he graduated from his studies as a Doctor of Law. In 1937 Uiberreither was leader of the illegal SA Brigade Steiermark, and in 1938 he became an SA Brigadeführer. That same year, which saw Austria's Anschluss with Nazi Germany, he also became the Commissary Police Director for Graz, and on 25 May 1938, he was appointed Gauleiter of Styria .
In 1939 Uiberreither married Käte Wegener (*1918), the daughter of Alfred and Else Wegener. They had four sons.
The years 1939 and 1940 were ones of military service for Uiberreither, who became a mountain trooper (Gebirgsjäger) and participated in the German landing in Norway. In April 1940, he was discharged from the Wehrmacht with the rank of lieutenant.
In 1940, Uiberreither became Reich Governor (Reichsstatthalter) of Styria, in 1941 Chief of the Civil Administration in the occupied areas of Yugoslavian "Lower Styria", and in 1942, also the Reich Defence Commissar for the Gau of Styria. In 1943, he was promoted to SA Obergruppenführer. In 1944 he was the leader of the Volkssturm in Styria, a last-ditch home guard set up on Martin Bormann's order's towards the end of the Second World War, and associated in Styria with the Nazi "Werwolf".
In 1947, Uiberreither fled when it became clear that there was the threat of being handed over to Yugoslavia. After this, there are clues to his having spent a while in Argentina before he eventually – as it is supposed – went to live with his family in Sindelfingen under a false name.
- Sworn statement from Siegfried Uiberreither in connection with the Nuremberg Trials
- Photos of Siegfried Uiberreither (skip down about 3/5 of page)