This is the footage which appears to show in the head after he declined a shot of the Irishman's whiskey.
The former UFC champion launched his Proper Twelve drink to much fanfare last year and has been on a relentless promotional push ever since.
The video above three shots of the whiskey at the Marble Arch pub in Dublin on April 6 this year.
He clinks glasses with one man but another declines the offer before McGregor appears to punch the man with his left hand, Mirror.co.uk reports.
The Irishman is then dragged away as the victim staggers on his stool, much to the shock of the staff behind the bar.
Gardai confirmed at the time that they were investigating the incident.
In April, a source said: "There was a bit of a commotion, he [McGregor] was acting the mick and there was an incident.
"The man that was allegedly assaulted is from Ballyfermot and drinks in the pub a good bit."
McGregor has not fought in the UFC since last October when he was submitted by lightweight champion Khabib Nurmagomedov.
He is expected to return to the octagon early next year.
Mirror Sport has contacted McGregor's representatives for comment.
Earlier this year, McGregor was accused of smashing and stealing Ahmed Abdirzak's phone outside a Miami Beach hotel.
He was arrested on March 11 with police stating alleged victim Abdirzak was taking a picture of McGregor outside a hotel when he slapped the man's phone out of his hand.
But in May Abdirzak dropped the lawsuit and reached an out-of-court settlement with McGregor.
