Schwarzenegger was interacting with fans during a skipping competition at his Arnold Classic Africa sporting event when a man drop-kicked him from behind.
The video footage, shared widely on social media, shows Schwarzenegger posing for photos and filming at the Johannesburg event on Saturday when the man attacks him with a flying kick.
The Terminator star stumbled forward after the kick, while the attacker falls to the ground, screaming, “Help me, I need a Lamborghini,” as he is immediately detained by the security guard following the incident.
The man was later handed over to police officers, event officials said.
Schwarzenegger thanked his fans on Twitter for their concern, but insisted there was “nothing to worry about.”
Schwarzenegger tweeted to his more than four million followers: “I thought I was just jostled by the crowd, which happens a lot. I only realized I was kicked when I saw the video like all of you.”