The pelagic thresher occurs in the tropical and subtropical waters of the Indian and Pacific Oceans, usually far from shore, but occasionally entering coastal habitats.

It is often confused with the common thresher (A. vulpinus), even in professional publications, but can be distinguished by the dark, rather than white, color over the bases of its pectoral fins.

Pelagic threshers are valued by commercial fisheries for their meat, skin, liver oil, and fins, and are also pursued by sport fishers.

The pelagic thresher was originally described by Japanese ichthyologist Hiroshi Nakamura on the basis of three large specimens, none of which was designated a holotype.

[5] However, it occasionally comes close to shore in regions with a narrow continental shelf, and has been observed near coral reef dropoffs or seamounts in the Red Sea and the Gulf of California, and off Indonesia and Micronesia.

This species has a fusiform body (wide in the middle and tapered at the ends) and a very slender upper caudal fin lobe nearly as long as the rest of the shark.

[5][6] The pelagic thresher is an active, strong swimmer and has been known to leap clear of the water (five times in a row on one documented occasion).

Known parasites of this species include the tapeworms Litobothrium amplifica, L. daileyi, and L. nickoli, which inhabit the shark's spiral valve intestine,[5] and copepods of the genus Echthrogaleus, which infest the skin.

[3] Analysis of stomach contents reveals that pelagic threshers feed mainly on barracudinas, lightfishes, and escolars, all inhabitants of the mesopelagic zone.

Therefore, little competition occurs between the pelagic thresher and other large oceanic piscivores such as billfishes, tunas, and dolphinfishes, which tend to feed near the surface.

The developing embryos are sustained by a yolk sac until they are 12 cm (4.7 in) long, after which they are oophagous and feed on egg capsules produced by the mother.

[13] Young pelagic threshers are born unusually large, up to 1.6 m (5.2 ft) long or 43% the length of the mother, which likely reduces predation on the newborns.

Furthermore, its aerobic red muscles, responsible for generating heat in the common thresher, are positioned in two lateral strips just beneath the skin rather than at the core of the body.

[15] The pelagic thresher has never been implicated in an attack on humans; it has small jaws and teeth for its size and tends to flee from divers.

[5] Pelagic threshers are frequently taken as bycatch on longlines and in driftnets meant for other species such as tuna, and also rarely in gillnets and antishark nets.