The supermodel (42) suffered a torn ligament in her left leg after she was robbed while hailing a cab in a busy street.
It is not known what was stolen but the muggers are believed to have targeted her jewellery. The attack happened last month, but has only now been revealed.
Campbell has been spotted wearing a leg brace and using crutches and a motorised wheelchair in recent weeks, but has not spoken about the mugging.
Vladimir Doronin, Campbell’s billionaire Russian boyfriend, has stepped up security around Campbell since the attack.
A source close to the model said, “It was terrifying. Naomi believes the assailant had been watching her, casing her out, and waited for a moment to strike when she was alone.
She was attacked in the street as she hailed a cab, and robbed. Her leg was injured as she was violently pushed to the ground. She was understandably very upset and shaken up.”
The model’s spokesman and agent declined to comment about the incident.