Harris joins in late October as director of comms and public affairs.
He will be responsible for the university's external and internal comms teams, and is expected to act as a high-profile spokesman for the institution.
He joins as Oxford and rival Cambridge reach the end of a six-year programme which monitors their reputation among teachers and students.
Last month outgoing comms boss Helen Carasso said that although the universities had succeeded in positioning themselves as 'academic rather than social elites', they still needed to change their pricey and limited-opportunity image.
Harris said it felt like 'the right time to take on a new challenge' after seven years at Lambeth Palace, which included serving under two archbishops.
His current role as Lambeth Palace's secretary for public affairs and deputy head of staff involves developing and managing the relationship between the archbishop's office, monarchy and government.
Harris previously spent 24 years at the BBC, working in its Madrid, Moscow and Washington bureaux before becoming foreign affairs correspondent.
Carasso is now Oxford's acting director of undergraduate admissions.