Jarrettsville is an unincorporated community and census-designated place (CDP) in Harford County, Maryland, United States. The population was 2,916 at the 2010 census.
The town was named for the Jarrett family, who farmed the area during the 1800s. My Lady's Manor was listed on the National Register of Historic Places in 1978, and includes portions of Jarrettsville.
Jarrettsville is located in northwestern Harford County at 39°36′7″N 76°28′21″W (39.601954, −76.472404). Maryland Route 23 passes through the center of the town, leading southeast 9 miles (14 km) to Bel Air, the county seat, and northwest 12 miles (19 km) to the Pennsylvania border north of Norrisville. Maryland Route 165 passes through the center of Jarrettsville as well, leading northeast 12 miles to the Pennsylvania border near Cardiff and south 8 miles (13 km) to Baldwin. Jarrettsville is 30 miles (48 km) northeast of downtown Baltimore.
According to the United States Census Bureau, the CDP has a total area of 8.6 square miles (22.4 km2), of which 0.03 square miles (0.07 km2), or 0.29%, are water.
As of the census of 2000, there were 2,756 people, 900 households, and 781 families residing in the CDP. The population density was 315.8 people per square mile (121.9/km2). There were 918 housing units at an average density of 105.2/sq mi (40.6/km2). The racial makeup of the CDP was 97.21% White, 1.16% African American, 0.15% Native American, 0.29% Asian, 0.33% from other races, and 0.87% from two or more races. Hispanic or Latino of any race were 0.54% of the population.