The Mildrith legend suggests that he was the younger son of Eadbald, and that his older brother Eormenred was deliberately passed over, although another possibility is that they ruled jointly.

According to Bede (HE III.8), Eorcenberht was the first king in Britain to command that pagan idols be destroyed and that Lent be observed. Eorcenberht married Seaxburh, daughter of king Anna of the eastern Angles, and their daughter Eorcengota became a nun at the abbey of Faremoutiers-en-Brie on the continent.

Eorcenberht was succeeded by his son Ecgberht.

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