[2][3] Scarus spinus can reach a total length of about 30 cm (in males).

Males show a bright yellow head underwater, while females are drab with white teeth and some pale spots.

Caudal fin is moderately to deeply emarginate in terminal phase.

Lips largely cover dental plates.

The Greensnout parrotfish inhabits coral-rich areas of outer lagoon and seaward reefs, at a depth range 0 - 30 m.[3] It appears specialized in scraping crustose coralline algae with its jaw.