The 32.79-square-kilometre (12.66 sq mi) lake lies on the river Otra, primarily in the municipality of Bygland, but the far southern tip of the lake extends into the neighboring municipality of Evje og Hornnes.

The villages of Byglandsfjord, Grendi, Longerak, Lauvdal, and Bygland are all located on the eastern shore of the lake along the Norwegian National Road 9.

The western shore of the lake is much more sparsely populated, with County Road 304 following that shoreline.

[1] The SS Bjoren is a wood-fueled steamboat that travels on the Byglandsfjorden in the summers between the villages of Ose (on the Åraksfjorden), Bygland, and Byglandsfjord.

There is a special relict species of salmon that live in Byglandsfjorden, called bleke.