Police were carrying out routine stop-and-search crime prevention duties when they stopped a couple who were intending to catch an Intercape bus to Cape Town, Captain Xoli Mbele said.
They searched the couple and found a firearm and ammunition in the woman's handbag. The firearm had no serial number.
When they asked her about the firearm she pointed to her husband, indicating "that it must be him who put it on her handbag".
Both were arrested for possession of an unlicensed firearm and ammunition.
The police investigation was under way and the two suspects, aged 32 and 39, would appear in the Johannesburg Magistrate's Court soon, Mbele said.