Tamsweg is located on the southern slope of the Schladminger Tauern mountain range within the Central Eastern Alps, in the valley of the upper Mur River, the driest basin in Austria.

The municipality consists of the cadastral communities of Haiden, Keusching, Lasaberg, Mörtelsdorf, Sauerfeld, Seetal, Tamsweg and Wölting.

In 1490, it was occupied by Hungarian troops of King Matthias Corvinus and became the site of violent fights against the armed forces of Emperor Frederick III.

The archbishops fought against the Protestant Reformation in their estates, in the course of the Counter-Reformation, Tamsweg was enlarged as an episcopal residence and its citizens vested with further market rights in 1587, especially concerning the trade with salt and iron.

The municipal assembly (Gemeinderat) consists of 25 seats and as of 2009 elections is composed of Iseo, Brescia, Lombardy, Italy Tamsweg lies at the junction of the Bundesstraßen (federal highways) B95 Turracher Straße from Mauterndorf to Predlitz-Turrach in Styria and the B96 Murtal Straße from Sankt Michael im Lungau and the A 10 Tauern Autobahn (European route E55) to Murau.