Hillandale is an unincorporated area and census-designated place located in Montgomery and Prince George's counties, Maryland, United States. As of the 2020 census, it had a population of 5,774. Hillandale is contained between the Prince George's/ Montgomery County line to the east, the Anacostia River to the west, McCeney Avenue to the north, and D.C.'s Capital Beltway to the south. It borders the communities of Adelphi, Avenel, White Oak and Beltsville.