The '#19 Legends' clash will take place at the home of Celtic to celebrate the ex-Aston Villa and Bhoys player, who was forced to retire from the game after undergoing treatment for acute leukaemia.
"I am delighted to play in this match and to be able to support such a worthy cause," Keane told Celtic's official website. "Stiliyan was a very gifted player and is a top lad.
"The way he has conducted himself throughout his battle with his illness is truly remarkable. I am sure there will be a tremendous atmosphere at Celtic Park and I'm looking forward to being part of it."
The event is scheduled for Sunday, September 8.