The sailfin molly was originally described in 1821 as Mollienesia latipinna by the naturalist Charles Alexandre Lesueur, who based his description upon specimens from freshwater ponds in the vicinity of New Orleans, Louisiana.

While most names that contain a "sail" element refer to the present species, the German Segelkärpfling, the Latin velifera, and possibly others are used for the Yucatan molly.

The sailfin molly is found in freshwater and brackish habitats from North Carolina to Texas and the Yucatán Peninsula of Mexico.

Preferring coastal marshes fed by lowland streams, as well as mangrove swamps, deltas and estuaries, the sailfin molly is very common in peninsular Florida and around the entire Gulf of Mexico.

[4] Sailfin mollies introduced to California[5] have caused a decline in populations of the federally protected and endangered desert pupfish (Cyprinodon macularius).

[6][7] It is also invasive to Iraq, where it thrives in the Persian Gulf waters at the confluence of the Tigris and Euphrates river deltas, threatening to outcompete many killifish species endemic to the region.

Small to large aggregations of the species are most commonly found under floating vegetation or near structures in the water, minimizing their chances of being observed by potential predators.

The sailfin molly is a tolerant species, as it can exploit the thin film of oxygen-rich surface water with its upturned mouth, so is able to survive oxygen-depleted habitats.

(See: Sexual selection) It is a smaller fish than the Yucatan molly (P. velifera), though that species often does not grow to full length if bred in an aquarium.

[6] Sailfin mollies feed primarily upon algae and other plant materials, although they will consume a number of aquatic invertebrates, including the larvae of mosquitoes.

Sailfin mollies produce broods of 10–140 live young, depending on maturity and size, and females may store sperm long after the demise of their relatively short-lived mates.

The gestation period for this species is about three to four weeks, depending upon temperature, and a single female may give birth on multiple occasions throughout the year.

Although sex ratios of the broods are balanced, adult populations tend to be largely female, as males appear to suffer higher rates of mortality due to a greater susceptibility to predators and disease as a consequence of their brighter colours and a life devoted to frenzied breeding.