Apolemichthys trimaculatus is a bright yellow species of angelfish which has blue lips, a wide black margin to the anal fin, a black spot on the forehead and a faint spot just to the rear of the operculum.

[3] Apolemichthys trimaculatus is widely distributed throughout the tropical waters of the Indian Ocean from the coast of East Africa between Tanzania and Mozambique to the western Pacific Ocean where it reaches as Far East as Samoa, as far north as southern Japan and as far south as New Caledonia.

[5] Apolemichthys trimaculatus is found at depths of 10 to 80 metres (33 to 262 ft) where it lives on outer coral reef slopes and drop-offs.

[6] The juveniles are more secretive and solitary than the adults and typically remain deeper than 25 metres (82 ft).

Adults are normally encountered at moderate depths in small, loosely organised groups.