The SA Revenue Services (Sars) said that the woman, "who arrived from Sao Paulo, initially denied checking in any luggage" on Thursday.
"However, when the officers enquired further, it was established that she had checked in luggage weighing 23kg," Sars said in a statement.
"The officers then found her checked-in bag on the carousel. During a physical inspection of the bag, two backpacks filled with 10.645kg of suspected cocaine were discovered and the woman was immediately detained."
Sars said it was making progress tracing those engaged in illegal activities "through months of intense surveillance and observing various flights".
The woman is expected to appear in the Kempton Park magistrate's court on a charge of drug smuggling.