Mechanicsville comprises the western portion of Hanover County's southern extension, north of the Chickahominy River. The southern border of the CDP, which follows the Chickahominy, is the Henrico County line, and at its closest point, Mechanicsville is less than two miles from the city limits of Richmond. U.S. Route 360 passes through the CDP, leading southwest to the center of Richmond and northeast to Tappahannock. Interstate 295, an eastern bypass of Richmond, crosses Mechanicsville from northwest to southeast, with access from exits 41, 38, 37, and 34. U.S. Route 301 forms the northwest border of the CDP, leading south to the center of Richmond and north to Bowling Green.