Pawcatuck is a census-designated place (CDP) in the town of Stonington which is located in New London County, Connecticut, United States. The population was 5,474 at the 2000 census. It is located across the Pawcatuck River from Downtown Westerly in Rhode Island. It includes the Mechanic Street Historic District, which is listed on the National Register of Historic Places. The historic district includes sites of shipbuilding, mills, and worker housing in a 147-acre (0.59 km2) area.
According to the United States Census Bureau, the CDP has a total area of 3.7 square miles (9.6 km2), of which, 3.7 square miles (9.6 km2) of it is land and 0.04 square miles (0.1 km2) of it (0.54%) is water.
As of the census of 2000, there were 5,474 people, 2,427 households, and 1,439 families residing in the CDP. The population density was 1,479.9 people per square mile (571.2/km2). There were 2,598 housing units at an average density of 702.4 per square mile (271.1/km2). The racial makeup of the CDP was 93.53% White, 0.75% African American, 0.69% Native American, 2.12% Asian, 0.05% Pacific Islander, 0.69% from other races, and 2.16% from two or more races. Hispanic or Latino of any race were 1.44% of the population.