"Markets are very jittery. There was a sell-off in European banks today and that's kind of spread through to our banks," said Sasfin equity strategist David Shapiro.
At 1603 GMT, the rand traded at 18.1600 against the dollar, about 0.4% weaker than its previous close.
The dollar index , which measures the currency against six rivals, rose around 0.5%.
The U.S. Federal Reserve on Wednesday delivered an expected interest rate hike of 25 basis points, but took a cautious stance on economic outlook due to the recent banking sector turmoil. Local investors will shift their focus towards the South African central bank's rate decision next week, with markets expecting a 25-basis-point hike. The government's benchmark 2030 bond weakened, with the yield up 0.5 basis points at 9.940%. (Reporting by Tannur Anders and Bhargav Acharya; Editing by Sherry Jacob-Phillips, Nellie Peyton and Richard Chang)