The 34-year-old played 37 Tests for the Proteas between 2007 and 2011, taking 103 wickets, while he also represented Warwickshire in the County Championship.
In South Africa he has played for Western Province, Northerns, Highveld Lions and Nashua Titans during a first-class career spanning 14 years.
Harris said: "I will be retiring from cricket at the end of the 2012/13 season. I would like to thank all the people who have helped me over my career. I am now going to enjoy being a Titans and Proteas supporter."