Katlego Marite was taken from the street in Witbank, Mpumalanga province, on Sunday, with his kidnappers leaving behind a note warning his parents not to contact the police.
In the note, the kidnappers demanded a ransom in bitcoins, which are difficult to trace, or they would kill their son.
His mother later told South African news site TimesLive they had no idea what bitcoins were.
It is unclear whether Katlego’s parents paid any ransom.
Brigadier Leonard Hlathi told local media the boy had been found alive in Witbank on Thursday, but would not be drawn on any further details.
Three people have been arrested in connection with the case.