Gray above and white below, the porbeagle has a very stout midsection that tapers towards the long, pointed snout and the narrow base of the tail. It has large pectoral and first dorsal fins, tiny pelvic, second dorsal, and anal fins, and a crescent-shaped caudal fin. The most distinctive features of this species are its three-cusped teeth, the white blotch at the aft base of its first dorsal fin, and the two pairs of lateral keels on its tail.

Most commonly found over food-rich banks on the outer continental shelf, it makes occasional forays both close to shore and into the open ocean to a depth of 1,360 m (4,460 ft). It also conducts long-distance seasonal migrations, generally shifting between shallower and deeper water.

The porbeagle is an opportunistic hunter that preys mainly on bony fishes and cephalopods throughout the water column, including the bottom.

The porbeagle is fast and highly active, with physiological adaptations that enable it to maintain a higher body temperature than the surrounding water. It can be solitary or gregarious, and has been known to perform seemingly playful behavior. This shark is aplacental viviparous with oophagy, developing embryos being retained within the mother's uterus and subsisting on non-viable eggs. Females typically bear four pups every year, born at about 70-80 cm. Depending upon location this animal is classified as Vulnerable (globally) and Endangered in the western North Atlantic,and Critically Endangered in the eastern North Atlantic and Mediterranean Sea.

A Treasury of New Zealand Fishes: Graham Stevens, J., S.L. Fowler, A. Soldo, M. McCord, J. Baum, E. Acuña, A. Domingo and M. Francis (2006). "Lamna nasus". IUCN Red List of Threatened Species. Version 2010.1. International Union for Conservation of Nature.