Epinephelus undulosus has a
standard length which is 2.7 to 3.1 times its depth. It has a convex region between the eyes. The preopercle is angular with an incision just above its angle and there are enlarged serrations at the angle while the gill cover has a straight or slightly concave upper margin. There are 11 spines and 17-19 soft rays in the
dorsal fin and 3 spines and 8 rays in the
anal fin. The membranes between the dorsal fin spines are not notched. The caudal fin is truncate or emarginate. The overall colour of the head, body, and fins purplish grey to brownish grey, marked with brown to golden-brown spots on the head and wavy horizontal brown or golden brown lines on the upper body, although these may be indistinct on larger fish. The margin of the spiny part of the dorsal fin has a thin line of blackish colouration. This species attains a
total length of , although they are more commonly around , and a maximum weight of . ==Distribution==