Merrifield is a census-designated place in Fairfax County, Virginia, United States. The population was 15,212 at the 2010 census. There were 4,396 households out of which 28.1% had children under the age of 18 living with them, 48.7% were married couples living together, 8.8% had a female householder with no husband present, and 38.0% were non-families. 25.0% of all households were made up of individuals and 3.5% had someone living alone who was 65 years of age or older. The average household size was 2.54 and the average family size was 3.06. The median income for a household in the CDP was $70,363, and the median income for a family was $74,116.