Like most snakes, rat snakes are egg layers. Between March and May, snakes begin to emerge from their winter hibernation. After a few weeks, they begin to seek out a mate, typically in late April, May, and early June. Males tend to wait for the females to pass through their territory, and, by using pheromones, communicate and initiate the mating process with the female. The male snake approaches the female, lines up with her, and attempts to wrap his tail around hers with their vents nearly touching. Some males grasp the female with the mouth,to hold her in place and prevent her from moving away. The male then erects his hemipenes and inserts it into the female's cloaca while several small spines anchor the hemipenes firmly. Mating may last only a few minutes or span a few hours.
Five weeks later, the female lays 12 to 20 eggs. The eggs are laid in a hidden area, under hollow logs or leaves, or in abandoned burrows. The eggs hatch 65 to 70 days later. The hatchlings of common rat snakes are vigorous eaters and double their size rather quickly. If conditions are good, females sometimes produce two clutches of eggs a year.