At 1532 GMT, the rand traded at 18.1700 against the dollar, 1.07% weaker than its previous close.
The local currency had steadied on Thursday, a day after a strong gain, as the markets digested South Africa's mid-term budget update on the government's finances.
On the local front, the rand was little swayed by South Africa recording a narrower budget deficit in September.
Emerging market currencies such as the rand have taken a hit this year as investors around the world scurry towards safe-haven assets, with appetite for riskier assets sapped by economic uncertainty amid aggressive monetary policy tightening by major central banks.
The dollar index, which measures the currency against six rivals, was last trading up nearly 0.3% at 110.87.
All eyes will be on the Fed's policy decision on Wednesday, when a 75 basis points hike is expected.
Shares on the Johannesburg Stock Exchange fell, weighed down by market heavyweights Naspers and Prosus. This mirrors similar moves in global equities as nearly $1 trillion in top tech stocks have been wiped out this week.
Overall, the Top-40 index closed 1.29% lower, while the broader all-share index ended down 1.1%.
The government's benchmark 2030 bond was weaker in early deals, with the yield up 7 basis points to 10.740%.
(Reporting by Anait Miridzhanian and Bhargav Acharya; Editing by Alex Richardson and Tomasz Janowski)
