Ezana's early coins carry the crescent and disc of the old gods; later issues carry the cross. His inscriptions change too, invoking the 'Lord of Heaven'.

Frumentius had been shipwrecked as a youth and brought to the Aksumite court. After the conversion, he was consecrated bishop in Alexandria, beginning a link between the Ethiopian and Coptic churches that lasted until 1959.

In the late 5th century the Nine Saints arrived from the Roman world. They founded monasteries, and the Bible was translated into Ge'ez, the classical language of the church.

In the 6th century Saint Yared created the zema — the system of sacred chant — and its musical notation, which remain at the heart of Ethiopian Orthodox worship.