The Massasauga rattlesnake is the smallest of the four kinds of rattlesnakes that have been recorded for Canada. It rarely exceeds 75 cm (29 in.) in length, although longer ones have been recorded.

A pair of long fangs at the front of the mouth are hollow and resemble short, curved hypodermic needles. Venom is injected into the snake's victims through these teeth. Because this poison may be toxic-enough to kill an adult human, antivenin is kept on hand at hospitals in its range. However, this shy snake generally retreats from a disturbance, and certainly does not seek confrontations with humans. It will often rattle and strike if threatened, but it will strike without warning only if surprised.

Females birth live young in late summer; usually there are 8 to 15 in a litter.

These snakes will inhabit low, swampy areas particularly in spring or autumn, but they often move to uplands in summer. They can locate prey by heat detection; they feed mainly on frogs and mice.

A subspecies of this snake occurs in Canada: the eastern Massasauga rattlesnake (Sistrurus catenatus catenatus). It occurs in Ontario from Windsor and the Niagara Peninsula north to Georgian Bay and east to the Muskoka Lakes. In the United States, it is found from central New York to Iowa and Missouri.