The town is situated in the Gegend valley (Gegendtal) of the Nock Mountains range (part of the Gurktal Alps), stretching to the eastern shore of Lake Millstatt.
Radenthein borders on the municipalities of Millstatt in the west and Bad Kleinkirchheim in the east.

The municipal area comprises the cadastral communities of Döbriach, Kaning, Laufenberg, Radenthein proper, Sankt Peter, and Tweng.
The town is situated in the Gegend valley (Gegendtal) of the Nock Mountains range (part of the Gurktal Alps), stretching to the eastern shore of Lake Millstatt. Radenthein borders on the municipalities of Millstatt in the west and Bad Kleinkirchheim in the east.
The municipal area comprises the cadastral communities of Döbriach, Kaning, Laufenberg, Radenthein proper, Sankt Peter, and Tweng.
Radenthein