Coordinates: 57°46′11″N 12°01′04″E / 57.76961°N 12.01787°E Lärjedalen is in the south of the former municipality Angered; it gets its name from the river Lärjeån that crosses the municipality.
Great parts of Lärjedalen are natural reserves.
The "center" of Lärjedalen is the suburb Hjällbo.