In the south the wooded Hochgosch plateau, with a breadth of 2 km (1.2 mi) and an elevation of 876 m (2,874 ft), divides the lake from the parallel Drava Valley.

The lake arose in the last glacial (Würm) period, about 20,000 years ago, when a northern offset of the Drava glacier melted in situ and left dead ice with extended fluvial deposits at its western rim damming meltwater.

The Millstatt area is part of the Austroalpine nappes, consisting of gneiss and schists with quartzite deposits, which arose by the metamorphism of sand and clay minerals, probably in the Ordovician period.

Today sport fishing and angling is quite common not only for trout but also for several genera of carps, for wels catfish, northern pike, zander, perch and the European eel.

The B98 Millstätter Straße highway runs along the northern shore of the lake, connecting it with the Tauern Autobahn (A10) motorway from Salzburg to Villach (part of the European route E55) at the Spittal/Millstätter See junction.