The Springboks, who are chasing a third straight World Cup title, will play the Fijians on September 18 next year before their tournament opener against Italy in Adelaide on October 3.
Springboks coach Rassie Erasmus said Fiji would present a tough test for his side.
“They are one of the top 10 ranked teams in the world, and they are a physical and talented side who will undoubtedly want to take full advantage of the match, similarly to us, before the Rugby World Cup kicks off,” he added.
South Africa and Fiji have met on three previous occasions with the Springboks winning all three. Their last meeting was at the 2011 World Cup.
The Springboks also have Georgia and Romania in Pool B at the World Cup, while Fiji open their campaign against Spain in Newcastle and later meet Canada and Argentina.