Analysts polled by Reuters had forecast that inflation would slow to 5.4% in annual terms.
The South African Reserve Bank (SARB) kept its main interest rate unchanged at 8.25% last month, saying its policy stance needed to remain restrictive to tackle higher inflation expectations.
It expects headline inflation to reach the midpoint of its target range of 4.5% only near the end of 2025.
SARB Governor Lesetja Kganyago told Reuters earlier in April that South African policymakers were in discussions to lower the bank's current inflation target range of between 3% and 6% to bring it more in line with peers.
On a month-on-month basis, inflation was at 0.8% in March compared to 1.0% a month before, Statistics South Africa said.
(Reporting by Bhargav Acharya; Editing by Alexander Winning)
