Suncook is a census-designated place in Merrimack County, New Hampshire, United States. The population was 5,501 at the 2020 census. Approximately two-thirds of Suncook is located in the town of Pembroke, with the remainder in Allenstown. The village of Suncook formed along the falls of the Suncook River, which drops 70 feet in one-half mile just before joining the Merrimack River.