The False Killer Whale was first known from a skeleton from Lincolnshire, England, and Owen named it Phocaena crassidens. A mass stranding in 1860 proved its continued existence (something that had been in doubt) and after examining the animals, Danish zoologist Johannes Reinhardt amended the classification to Pseudorca crassidens, referring to this cetacean's resemblance to the Orcas (Killer Whale). The specific name, crassidens, means 'thick-tooth', and is a reference to this species' robust teeth. This species is quite separate to the Orca.

The False Killer Whale is a small and slim cetacean, with a tapering, rounded snout that overhangs the lower jaw, upon which there are between 8-11 pairs of teeth, matching the upper jaw. Above the mouth line, a crease trails from below the eye to the tip of the head. The dorsal is curved and located around halfway along the rounded body. The flippers have a broad hump on the leading edge which resembles a shoulder. The body color is predominantly black, save for the odd faint gray marks on the head and throat. Males and females reach a maximum length of 5.96m and 5.1m respectively. Maximum weight in males is 2.2 tons; in females, 1.1 tons.

The False Killer Whale can be identified by their size and head shape; the latter and the shape of the dorsal are also useful in distinguishing them from Pilot Whales. Also, this is the only 'Blackfish' to bow-ride and swim rapidly at the surface.

False Killer Whales tend to prefer warm temperate, subtropical and tropical waters, mainly in either semi-enclosed seas or in the open ocean away from land. Occasionally individuals have been spotted as far north as the northern UK, Norway and Alaska.

False Killer Whales prey mainly upon squid and large fish (such as tuna and dolphin fish), but have been known to attack groups of small cetaceans. This species has a bad reputation for taking bait from fishermen's lines. The typical family unit contains between 10-50 individuals, but this cetacean is highly social and groups of several hundred are also common.

A fast-swimming species, the False Killer Whale often gets excited, and porpoises (leaping clear of the water whilst swimming), bow-rides, and chases faster vessels. It has adapted well to captivity and is easily trained, showing much less aggression that the Pygmy Killer Whale. Mass stranding are common; in one case, over 800 individuals were found ashore.