The South African Chamber of Commerce and Industry's (SACCI) monthly business confidence index (BCI) increased to 97.0 in May from 94.7 in April.
The May BCI level was the highest since March 2018 when the BCI measured 97.6.
"The BCI points towards an improving business climate. This can however mainly be ascribed to an improved trade balance that positively affected the rand exchange rate which in turn took pressure off cost-push inflationary pressures," SACCI said in a statement.
SACCI said a rise in merchandise export volumes was the main positive contributor to the BCI, and to a lesser extent manufacturing output and consistent energy supply during the month.
South Africa's economy is slowly on the mend after suffering a steep contraction of 7% in 2020 due to the COVID-19 pandemic.
Data on Tuesday showed the economy grew 4.6% quarter-on- quarter on a seasonally adjusted and annualised basis in the first three months of 2021, beating expectations.
(Reporting by Olivia Kumwenda-Mtambo; Editing by Promit Mukherjee)