Harewood was born in the Small Heath area of Birmingham on 8 December 1965, the son of a couple from Barbados who had moved to England in the late 1950s and early 1960s. His father was a lorry driver, while his mother was a caterer. He has a sister, Sandra, and two brothers, Rodger and Paul. He attended St Benedict's Junior School and Washwood Heath Academy. He was a member of the National Youth Theatre. In his youth, he worked at a wine bar in Birmingham city centre. At the age of 18, he gained a place at the Royal Academy of Dramatic Art.