The blackside hawkfish reaches to a maximum total length of about 22 cm (9 in). The dorsal fin has ten spines and eleven soft rays, while the anal fin has three spines and six soft rays. There is considerable variation in the colouring both among adults and as a result of changes during growth. The main colour is usually yellowish but there is a broad black or dark brown lateral band, mainly on the rear half of the body. The sides of the head and the front of the body are whitish or grey, with red speckles. In Asia, juveniles may be reddish dorsally, while in Oceania they tend to have golden-green upper parts and white underparts. The blackside hawkfish is native to the tropical and sub-tropical Indo-Pacific Ocean. Its range extends from East Africa and the Red Sea to Japan, New Caledonia and Australasia. In Australia its range extends from the northwest of Western Australia round the north of the country to the border of Queensland and New South Wales. It is found on the seaward side of reefs and on soft-bottomed lagoons to depths of 30 m (100 ft) and more.
