Alagiah was born in Colombo, Ceylon on 22 November 1955. His parents, Donald Alagiah, an engineer, and Therese, were Sri Lankan Tamil. In 1961, his parents moved to Ghana in West Africa, where he had his primary education at Christ the King International School. He has four sisters. His secondary education took place at St John's College, an independent Roman Catholic school in Portsmouth, England, after which he read politics at Van Mildert College, Durham University. Whilst at Durham, he wrote for and became editor of the student newspaper Palatinate and was a sabbatical officer of Durham Students' Union.
