Roberta Kerr will reprise her role as Wendy on the ITV soap, which she appeared in between June 1989 and May 1990.
Wendy, then a council worker, won Ken's heart by laying on a surprise meal for his birthday. Their affair led to Ken's divorce from Deirdre.
Ken and Wendy are stunned when they bump into each other at Weatherfield's primary school, where it turns out they are both running for the role of new governor, revealed ITV.
Though adamant that they should remain good friends, Ken keeps Wendy's return to the area a secret from Deirdre.
Producer Phil Collinson said in a statement: "Ken's affair with Wendy was one of Coronation Street's defining stories during the '80s.
"Viewers were on the edge of their seats as they watched the disintegration of the Barlows' marriage and over 20 years later I hope they will be again.
"I'm delighted to welcome Roberta back as Wendy and can assure viewers that her reunion with Ken will be one of many must-see storylines this summer."
Roberta Kerr is also known for her time on fellow ITV serial Emmerdale, in which she portrayed Jan Glover for four years from 1994 until 1998.