Jarrettsville is a census-designated place (CDP) in Harford County, Maryland, United States. The population was 2,756 at the 2000 census.
My Lady's Manor was listed on the National Register of Historic Places in 1978, and includes portions of Jarrettsville. The town was named for the Jarrett family, who farmed the area during the 1800s.
Jarrettsville is located at 39°36′7″N 76°28′21″W / 39.60194°N 76.4725°W / 39.60194; -76.4725 (39.601954, -76.472404).