Hamoor chlorostigma can reach a length of 12–75 cm and a weight up to 7 kg. It is one of the largest coral dwelling fish. It has large pectoral and caudal fins that enable it to move and maneuver quickly through the water. It has a pale green gray body covered with small circular brown blotches, except for its belly which is lighter in color. When aroused, the fish is able to change its body shading according to its surroundings. Five dark brown vertical bands appear along the body. Its mouth is very large and capable of being opened to the width of the body diameter.