Body robust, elongate, the greatest width more than half of body depth, which is distinctly less than head length (in fish 15 to 160 cm); body depth contained 2.7 to 3.4 times in standard length. Head length contained 2.3 to 2.9 times in standard length; head extremely broad; interorbital flat, the width equals eye diameter in fish 10 to 15 cm standard length, distinctly greater than eye diameter in fish 18 to 25 cm standard length, and 1.5 to 3.4 times greater than eye diameter in fish 30 to 160 cm standard length; eye diameter contained 5 to 8 times in head length for fish 10 to 30 cm standard length and 8 to 13 times in head length for fish 35 to 160 cm standard length; preopercle rounded, finely serrate; nostrils round, subequal; maxilla scaly, reaching well past eye; midlateral part of lower jaw with 3 to 5 rows of subequal teeth; no canines at front of jaws. Gill rakers 8 or 9 on upper limb and 13 to 15 on lower limb, total 21 to 24; gill arches covered with small bony plates. Dorsal fin with XI spines and 15 or 16 rays, the spines short, 3rd to 11th subequal and shorter than the first ray, the membranes distinctly indented between the spines; anal fin with III spines and 8 rays; pectoral-fin rays 18 or 19; caudal fin rounded. Body scales strongly ctenoid; lateral-line scales 61 to 64, each with 4 to 6 radiating ridges; lateral-scale series 89 to 112.
Colour: Generally brownish yellow, grey, or greenish; head, dorsal part of body, and fins with small black spots, becoming smaller with growth. Fish less than about 1 m show 3 or 4 faint, irregular, subvertical dark bars posteriorly on body; and another covering rear half of caudal peduncle; large adults darker and more uniformly coloured than juveniles.

Tropical and subtropical waters of the Atlantic and eastern Pacific oceans. In the western Atlantic, it ranges from Florida to southern Brazil, and is caught widely in the Gulf of Mexico and most of the Caribbean. In the eastern Atlantic, E. itajara is reported (as Epinephelus esonue) by Séret (1981) and Smith (1981) from Senegal to the Congo; according to Brito (1991) it is rare in the Canary Islands. In the eastern Pacific, it occurs from the Gulf of California to Peru.

This giant grouper is often found in shallow water; juveniles are common in mangrove swamps and both juveniles and adults occur in bays and harbours. Large adults are also encountered offshore on wrecks and in areas of high relief; they appear to occupy limited home ranges with little inter-reef movement, and the same individuals were seen at specific reef sites for more than a year (G.B. Smith, 1976). Schroeder (1924) found that spawning occurred in July and August in the vicinity of Key West, Florida and the greater numbers of large adults captured at this time indicated that the local fishermen were probably exploiting spawning aggregations of this species. G.B. Smith (1976) observed what may have been a spawning aggregation of 20 to 30 large adults (45 to 200 kg) during a dive on a wreck in 36 m off the west coast of Florida in June 1971. Bullock and Smith (1991) estimated batch fecundity for two females of 132 and 140 cm standard length at 37 to 40 million and 55 to 58 million oocytes, respectively. Bullock et al. (1992) studied age, growth and reproduction of this species from the eastern Gulf of Mexico. Growth averaged >100 mm/year until the age of 6 years, when sexual maturity is attained at a size of 110 to 115 cm total length for males and 120 to 135 cm for females; growth then declined to about 30 mm/year at age 15 (182 to 191 cm total length), and to <10 mm/year after age 25. Age data from 382 fish were used to calculate the von Bertalanffy growth equation: total length (mm) = 2006 (1-e(1-0.126(age+0.49))). The oldest fish in their sample was 37 years and measured 197 cm total length. The peak spawning activity occurred during July to September. Contrary to reports for other groupers, Bullock et al. (1992) found that males of E. itajara are mature at a slightly smaller size and younger age than females, and they found no conclusive evidence for protogyny in this species. Adults and juveniles feed heavily on crustaceans (shrimps, crabs, and lobsters), and in the Caribbean, E. itajara is an important predator of lobsters. E. itajara take octopus, fishes (including stingrays, ariid catfishes, spadefish, parrotfish, diodontids and ostaciids), and young sea turtles.

E. itajara and E. lanceolatus of the Indo-Pacific region are the two largest species of grouper. The maximum size for this species is about 250 cm total length and at least 320 kg. The IGFA all-tackle record (as of 1991) is 308 kg. Bullock et al. (1992) gave the following weight/length formula for 66 jewfish: W = 1.31 x 10-8L3.036, where W is whole weight (kg) and L (total length) in millimetres.

E. itajara and E. lanceolatus of the Indo-West Pacific region have usually been recognized in the genus Promicrops, but Heemstra and Randall (1993) agree with Smith’s (1971) decision to include these two species in Epinephelus. These two species differ from other species of the genus by having the tubes of the lateral-line scales with 4 to 6 radiating branches.Except for large adults of E. malabaricus and E. coioides (which have a few anterior lateral-line scales with branched tubules), the lateral-line scales of other Epinephelus have unbranched tubes. Although Heemstra and Randall (1993) doubt that E. itajara of the eastern and western Atlantic and the eastern Pacific share a common gene pool, Heemstra and Randall (1993) are unable to find any significant differences in the published data or the specimens that they have examined from these three areas. If there is any species of American grouper that occurs on both sides of the Central American Isthmus, it would be E. itajara. It seems feasible that juveniles, with their predilection for estuarine and mangrove habitats, could easily traverse the Isthmus via the Panama Canal. Johnson and Keener (1984) illustrated the second dorsal- and pelvic-fin spines of the larvae.