The good news is the hulking man mountain got right back up onto his feet and climbed back up on stage and, like a true professional, completed his guest posing appearance.
"I did fall off the stage, I didn't see the edge," O'Hearn said to Generation Iron.
"I did instantly get up and continue my performance. quite embarrassing, but life is great that it will knock you down [and] always keep you humble.
"I can appreciate the little things. the show must go on. some bumps and bruises, but I will be fine."
He decided to have some fun with it all and joked not only was he fine, the floor didn't feel any ill effects.
"Please don't worry. I didn't break the floor," O'Hearn wrote on one post.
O'Hearn's Instagram feed is littered with images and videos of him busting out in the gym and posing alongside former Mr Universe Arnold Schwarzenneger in another post.
A self proclaimed natural bodybuilder, O'Hearn has come under constant criticism from fans who don't believe his physique could be natural. He's set to feature in an upcoming documentary on natural bodybuilding which is to be released in 2020.
