Relations between northern Ethiopia and South Arabia in Antiquity have been much discussed, most publications focusing on the first millennium BC. Relations during the first millennium AD have received less attention, apart from studies of dramatic events during the 6th century. A general framework of these contacts is proposed, along with new observations about contacts between the two sides of the Red Sea, in particular from the 1st to the 6th century AD. During ancient times, the two cultures seem, at first sight, to be quite different; but a closer look at the evidence from inscriptions and excavations (architectural features and building techniques) discovers that the two areas maintained contacts, which varied over time, and often evolved in like manner.