The win covers markets including Italy, France, The Netherlands and Australia as well as the UK.
The account was previously handled by Mediaedge:cia, which was appointed to the business in 2004. The WPP-owned agency did not repitch.
Ed Baxendale, Starcom's international account director, said: "South Africa is a key growth market both in economic and consumer terms and one that we are proud to be associated with. As a network, this is an excellent endorsement of Starcom's ability to deliver insightful, highly targeted solutions quickly and efficiently across markets to our multinational clients."
The win comes during a difficult period for Starcom. Earlier this week, the agency failed in a repitch for the Department for Work and Pensions' £7 million benefit fraud media brief.
The business was awarded to MindShare following a competitive pitch that also included Naked Communications and Ingram.
Starcom also lost the £2 million buying account for the New Covent Garden Food Company to Media Planning Group.
The South African Tourism Board's £21.1 million global advertising account is handled by TBWA\Worldwide.