In parts of its range, western blue-eyed grass has previously been classified as Sisyrinchium eastwoodiae, S. greenei and S. hesperium, but these names are now considered synonyms.

Sisyrinchium bellum grows as a perennial plant in open places where there is some moisture, particularly grassy areas, though it can also be found in woodlands and at altitudes up to 2,400 metres (7,900 ft).

The flowers are 1–2 centimetres (0.39–0.79 in) in diameter and purplish-blue, varying somewhat in color from a true blue to a definite purple; occasional white-flowering plants are found.

Sisyrinchium bellum prefers some moisture and good drainage, but will tolerate summer dryness.

The Ohlone used an infusion of the roots and leaves as a cure for indigestion and stomach pain, and similar uses are recorded from other Native American peoples.