Born near Kampala in Uganda, Sentamu studied law at Makerere University before gaining employment as an advocate of the Supreme Court of Uganda. Speaking out against the regime of President Idi Amin, he was briefly imprisoned before fleeing in 1974 to the United Kingdom, where he devoted himself to Anglicanism, beginning his study of theology at Selwyn College, Cambridge, in 1976 and eventually gaining a doctorate in 1984. He studied for ordination at Ridley Hall, Cambridge, and was ordained in 1979.