The incident occurred in a city pub when Henson joined a number of fellow Bath players on a night out.
CCTV footage appears to show the controversial Welsh international confronting a teammate in the Pig and Fiddle pub before being knocked to the ground by one punch.
Police were called to the premises following reports of aggressive behaviour, but no officers were sent out after the group moved on while the call was being made.
Bath have confirmed that they are investigating the incident.
You can watch a video of the incident below.