The aerodynamic shape and lightness of the blue shark body allow it to move “elegantly” across the oceans. It exhibits countershading like many other sharks. The upper part is an indigo blue tone while the ventral and the sides are white.
It has a long caudal heterocercal fin. The second dorsal fin measures almost half the size of the first and its pectoral fins are unusually long compared to other sharks. Its eyes are large, its teeth are triangular, and it has a conical snout.
It reaches a length ranging from 3.8 to 4 meters and weighs about 240 kilograms. This species presents slight sexual dimorphism since the female tends to measure little more than 1 meter in comparison with the male.