The rand was down 0.45% at 14.5500 against the dollar at 1500 GMT, retreating from a session high of 14.4500 earlier in the session.
The continent's most industrialised economy has been gripped by some of the worst violence in decades after the jailing of former President Jacob Zuma.
The government has deployed more soldiers in two provinces where security forces were struggling to quell looting, arson and violence.
The unrest threatens to derail one of this year's star emerging market performers and highlights the chronic joblessness and poverty that has been papered over by a short-term export boom.
"The rand remains vulnerable against the current local backdrop," Nedbank analysts said in a note.
Shares on the Johannesburg Stock Exchange (JSE) softened on Thursday as investors treaded cautiously after riots and looting in the country receded but the U.S. market, which affects the performance of almost 80% of local stocks, retreated from record highs.
The benchmark all-share index dropped by 0.53% to 67,539 points and the top 40 companies index lost 0.51% to 61,439 points.
The losses were broad-based as almost all major sectors retreated from the previous day's gains, with commodities and construction stocks posting the biggest fall of over 1%.
In fixed income, the yield on the benchmark 2030 government bond dipped 3.5 basis points to 8.955%, reflecting firmer prices.
(Reporting by Olivia Kumwenda-Mtambo and Promit MukherjeeEditing by Sonya Hepinstall)
