Growing to a maximum length of 4.3 m (14 ft), the slimmer build and long, broad pectoral fins of this shark suggest that it is a slower and less active swimmer than the shortfin mako.

Whether this shark is capable of elevating its body temperature above that of the surrounding water like the other members of its family is uncertain, though it possesses the requisite physiological adaptations.

The longfin mako is of limited commercial value, as its meat and fins are of lower quality than those of other pelagic sharks; however, it is caught unintentionally in low numbers across its range.

The International Union for Conservation of Nature has assessed this species as endangered due to its rarity, low reproductive rate, and continuing bycatch mortality.

[3][4][5] The original description of the longfin mako was published in 1966 by Cuban marine scientist Darío Guitart-Manday, in the scientific journal Poeyana, based on three adult specimens from the Caribbean Sea.

However, the type specimen designated by Glückman consists of a set of fossil teeth that could not be confirmed as belonging to the longfin mako, thus the name paucus took precedence over belyaevi, despite being published later.

[8] Fossil teeth belonging to the longfin mako have been recovered from the Muddy Creek marl of the Grange Burn formation, south of Hamilton, Australia, and from Mizumani Group in Gifu Prefecture, Japan.

[13] This species has a slim, fusiform shape with a long, pointed snout and large eyes that lack nictitating membranes (protective third eyelids).

This system enables other mackerel sharks to conserve metabolic heat and maintain a higher body temperature than their environments, though whether the longfin mako is capable of the same is uncertain.

[12] As in other mackerel sharks, the longfin mako is aplacental viviparous and typically gives birth to two pups at a time (one inside each uterus), though a 3.3-metre-long (11 ft) female pregnant with eight well-developed embryos was caught in the Mona Passage near Puerto Rico in January 1983.

[11] The developing embryos are oophagous; once they deplete their supply of yolk, they sustain themselves by consuming large quantities of nonviable eggs ovulated by their mother.

The pups measure 97–120 cm (3.18–3.94 ft) long at birth, relatively larger than the young of the shortfin mako, and have proportionally longer heads and pectoral fins than the adults.

[12][15] The most significant longfin mako catches are by Japanese tropical longline fisheries, and those sharks occasionally enter Tokyo fish markets.

From 1987 to 1994, United States fisheries reported catches (discarded, as this species is worthless on the North American market) of 2–12 tons per year.