Kuhlia mugil has a compressed body which is shaped like an elongated oval with a large eye and an oblique mouth which has a projecting lower jaw.

It is normally silver in colour, although the upper flanks sometimes show a bluish, brownish or yellowish tinge.

[4] There is a dusky band along the margin of the soft rayed portion of the dorsal fin except for a white tip on the highest anterior part.

[5] In the eastern Pacific they are found at the tip of Baja California and along the coast from Costa Rica to Colombia.

[2] This species occurs on reefs at depths of 3 to 18 m (9.8 to 59.1 ft), where they form tightly packed schools.