Möderbrugg is situated at an elevation of 970 m in the Pöls valley between the foothills of the Niedere Tauern mountain region in the Murtal district (combined in 2012 out of the districts Judenburg and Knittelfeld) in Upper Styria. Möderbrugg is one of the six cadastral communities of the municipality Pölstal.
The municipality of Sankt Oswald was founded in 1849/50.
On 1 June 1951 Sankt Oswald was renamed Sankt Oswald-Möderbrugg.
On 31 December 2014 the municipalities of Sankt Oswald-Möderbrugg, Bretstein,
Sankt Johann am Tauern and Oberzeiring were merged into the new municipality of Pölstal.