Melon is relatively flat and defined posteriorly by an indentation at the blowhole. The beak is thick and short with a massive lower jaw that rises prominently on either side of the rostrum about halfway along its length. The mouthline is strongly arched.
Adult males are dark blue-black with a grayish saddle that extends posteriorly from just behind the blowhole for about half the length of the dorsum. The leading edge of the dorsal fin may also be gray. The snout and lower jaws are white or pale gray for up to half the length of the jaw or to just past the teeth. Some individuals have a whitish patch on either side of the forehead at the base of the rostrum. The throat grooves are white or pale gray and the flipper pocket is also lighter in color. Sexually mature males of this species often exhibit scarring from antagonistic sparring. Other oval scars, attributed to the cookie cutter shark, Isistius brasilensis, are present especially in the posterior ventral area of adults.Females have a slate gray dorsum with flanks and belly pale gray to white. There is less white on the beak than in males.
Adult body length ranges between 3.9 to 4.9 m. Recorded maximum body length for adult males and females is 4.6 m and 4.9 m, respectively. Body length at birth is 2.2 m.
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