The Atlantic sailfish is a metallic blue fish with a large sail-like dorsal fin and a long and pointed bill-like snout. It is dark bluish-black on the upperparts and lighter on the sides (counter-shading), with about twenty bluish horizontal bars along the flanks; the underparts are silvery white. The tail fin is strongly forked. The fins are bluish-black and the front dorsal fin is speckled with small black spots. The bases of the anal fins are pale.
The length of this fish is up to 3.15 m (10.3 ft) and the maximum published weight is 58.1 kg (128.1 lb).