This is a small, elongated fish with a light brown or tan body. It has a dark brown to black stripe that runs from the tip of its snout to its peduncle, crossing its large, dark eyes. It has a black eye spot at the base of its tail fin. With maturity the first ray of their dorsal fin turns bright yellow, whereas very young iridescent cardinals (like the one pictured) retain some yellow-green colouring on their head and belly.
Viewed under artificial light, iridescent shades of blue and green are visible on their body.
Iridescent cardinalfish inhabit clear waters surrounding reefs, where they take shelter in small caves and overhangs. At night they emerge to feed on small swimming and bottom-dwelling crustaceans.
These cardinalfish are solitary animals, only pairing briefly to spawn.
Iridescent cardinalfish have a wide range, from the Red Sea and South Africa to New Zealand, Japan and Hawaii.