The footage was filmed as the vlogger was practising for a "slapping competition" in Russia that he had been due to take part in.
Mr Paul now says he will pulll out of that competition, in order to avoid "serious injury".
The video, which was shared by Mr Paul himself, shows him readying to slap another man. He then hits him in the side of the face, and the man falls to the ground straight away.
The YouTube star had been due to take part in the competition this week, but has since announced on his Twitter account that the incident forced him to pull out.
"Due to an unforeseen and unfortunate event that took place during practice today, I have decided not to participate in the upcoming slap competition. Based on today's incident and the aftermath, it became clear that I don't have the desire to participate in an event that can result in serious injury to virtually anyone competing.
"I have the deepest respect for the sport and athletes involved; however, I feel my decision will preserve the health and wellness of everyone competing.
"I appreciate you taking the time to include me in the process and will absolutely continue to support the sport and organisation as a fan."
It is far from the first time that Mr Paul has courted scandal after being involved in dangerous stunts and pranks. Perhaps most infamous of all was a video he posted where he joked and laughed in front of a dead body.
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