Castle Hayne is a census-designated place (CDP) in New Hanover County, North Carolina, United States. The population was 1,234 at the 2020 census, up from 1,202 in 2010. Castle Hayne is located in the statistical township of Cape Fear. The CDP is part of the Wilmington Metropolitan Statistical Area. Castle Hayne was first listed as a CDP at the 1980 United States census.