Unlike other members of Scomberomorus, the King mackerel (Scomberomorus cavalla) lacks a black area on the anterior portion of the first dorsal fin. The King mackerel has 12-18 spines in its first dorsal fin; 15-18 rays in the second dorsal fin, which are followed by 7-10 finlets; and 21-23 pectoral fin rays. Its body is about five times the size of its head, and about six times as long as it is deep.

The entire body is covered with rudimentary scales, except for its pectoral fin. A unique feature of the King is the lateral line which drops sharply after the second dorsal fin, and then continues on to the tail. distinguishing it from the Cero mackerel (Scomberomorus regalis). The King mackerel also lacks scales on the pectoral fins as does the Spanish mackerel (Scomberomorus maculatus), in contrast to the cero mackerel which has scales extending onto the pectoral fin.