The port-city of Adulis in modern Eritrea was a key node on the Red Sea linking the Kingdom of Aksum to the Mediterranean, the Middle East and the Indian Ocean. Recent excavations at Adulis have reinvestigated two early Christian churches. New radiocarbon analysis dates both structures to the sixth and early seventh centuries AD, with multiple phases of architectural development reflecting changing use and liturgy. The author uses evidence for both continuity and change in architectural materials, construction styles and sacred practices to assess religious transition at Adulis, and across the Aksumite Kingdom more broadly. Moving beyond an archaeology of conversion, the article reinforces recent work on cosmopolitanism in the Horn of Africa.