It lies at an elevation of 529 m (1,736 ft) and covers an area of 517 km2 (200 sq mi), not including 79 km2 (31 sq mi) occupied by islands within the lake such as Grande Île[3] or Grosse Île.

The Quebec North Shore and Labrador Railway runs along the lake's eastern shore, and the Trans-Labrador Highway crosses the Ashuanipi River about 10 km (6.2 mi) north of the lake's northern terminus.

[7] The Lac Joseph caribou herd can be found around Ashuanipi Lake during the summer and fall.

[7][8] The lake is mainly surrounded by forests of black spruce,[7] although the Kapitagas Channel at the southern end of the lake features the only jack pine forest in Labrador and is protected as part of Redfir Lake–Kapitagas Channel Ecological Reserve.

[9] Through radiocarbon dating, evidence has been found at the lake for human habitation as far back as 1600 years ago.