The incident happened on Tuesday night and the boy, Mongezi Phike, was still missing, said an unnamed family friend, Beeld reported on Saturday.
Phike and his father were in a car at an intersection in Masada, Bronkhorstspruit, when four men approached.
Two of them were armed.
The gang allegedly tied the father’s hands and feet with wire, covered his head with a plastic bag and wrapped tape around his neck, the friend said.
His identity document, wallet, credit cards and phone were taken.
The friend said the father was hit on the head and left for dead at a construction site, while the hijackers fled with Phike.
He was later found and taken to a hospital in Delmas.
Bronkhorstspruit police spokeswoman Captain Sarah Mcira could not immediately be reached for comment.