The WPP-owned agency will work with the South African specialist communications agency Nota Bene, which has been appointed to handle the global communication strategy.
The account will be co-ordinated by Mediaedge:cia South Africa and then rolled out into its network in the relevant markets. South African Tourism, which made the appointment following a pitch involving 27 South African agencies, has identified 13 key tourist markets worldwide.
The body spent £1 million through OMD UK in the past 12 months, according to Nielsen Media Research.
Cheryl Carolus, the chief executive of South African Tourism, said: "Our new partners represent the best in their field. All have shown an impressive capability in competing, and winning, against some of the best agencies in the world. All possess the passionate commitment we expect from our partners in taking South Africa Tourism to new heights."