The 'Monster' star was heading into the ceremony at the Dolby Theater when a man working at the event fell to the ground, reported E! Online.
Theron rushed to the security guard's aid as another onlooker phoned a doctor.
The 37-year-old actress didn't let the drama affect her appearance at the ceremony - she teamed up with Channing Tatum to perform a ballroom routine while host Seth MacFarlane sang Fred Astaire's 'The Way You Look Tonight'.
"(It was) completely nerve-wracking, but how could I not dance with Channing Tatum? He's so wonderful!