He served as an Ealdorman in southern Mercia in the reigns of Kings Eadwig and Edgar.
Æthelflæd was a woman of considerable influence, and not merely as a relict of King Edmund; her father Ælfgar is described as a dux and Ealdorman of Essex.
Æthelstan appears to have had lands in Buckinghamshire and Oxfordshire.
He is a frequent witness to charters of Kings Eadwig and Edgar.
The Life of Saint Dunstan records a vision by a nobleman named Æthelstan and Dunstan's interpretation of it as presaging the death of the king and ill times to come.