A rattlesnake reproduces when a male presses his tail beneath a female's tail to inseminate the female. This is accomplished over several hours when the male lays on top of the passive female and makes jerking motions with his hind portion. The female can carry male sperm for up to six months to fertilize eggs at any time over that span.

Rattlesnake babies are born live after a gestation period of 90 days. The eggs hatch inside the mother's body and baby snakes crawl out; this is different from other snake species, which typically lay eggs in nests before birth. Female rattlesnakes carry between four and 25 eggs at a time, with an average birth of nine to 10 babies. Babies are born in spring or fall, and females reproduce every two to three years.

A baby rattlesnake is about 10 inches long when born. Instead of a rattle, a baby has a small nub on the end of its tail; the rattle grows in later. A baby rattlesnake has short fangs and venom when it hatches. The reptile is completely independent of its mother when born, and a baby rattlesnake leaves the area of its birth within 10 days of hatching. A rattlesnake reaches maturity in three years.