This species is known to have the greatest sexually dimorphic size disparity found in any North American turtle. Males are usually smaller in both body and head size, while the females are large. Females often attain carapace length of 9 inches, while males usually reach a maximum of 5.5 inches. They use the ridges in their jaw to crush their prey. While all turtles reproduce by eggs, the genus Malaclemys usually does not produce more than 4-8 eggs in a clutch.
Females typically nest several times annually.
The duration of incubation varies between 60 and 85 days, depending on soil temperature and nest depth. During April and May, the female digs a nest cavity 4-8 inches deep in sand. Wild hatchlings may spend their first years upstream in creeks. These creeks may either be brackish or relatively fresh water. As the hatchlings age, they move down to the salty marshes where nutrients and good nesting sites are plentiful.