The slender fusilier was first formally described in 1856 as Caesio gymnopterus by the Dutch ichthyologist Pieter Bleeker with the type locality being given as Ternate.

The back and upper flanks are bluish green in colour, with centres of scales paler, creating a striped appearance.

There is frequently a vivid blue horizontal band directly underneath the lateral line stripe taking up as much as one third of the flanks.

[7] The slender fusilier is found in the Indian Ocean from the southern Red Sea to South Africa, eastwards through the Seychelles and Mascarenes to the Maldives and Laccadives, Sri Lanka and southern India eastwards as far as Fiji in the Pacific Ocean.

[1] It occurs in coastal waters in the vicinity of coral reefs[7] at depths down to 500 m (1,600 ft).