Michael Chiesa is going after the Irishman for assault and battery after he was allegedly injured when a trolley was thrown through a bus window during a UFC event at the Barclays Centre in New York, The Sun reports.
McGregor and his associates stormed the arena in April in order to target Khabib Nurmagomedov, who he is fighting next month at the UFC 229.
But Chiesa was caught up in the brawl as he sat in the same vehicle as McGregor's nemesis.
And he was forced to miss his fight against Anthony Pettis two days later after sustaining cuts to his face.
Chiesa also required further hospital treatment, and TMZ claims he has now filed a lawsuit in New York.
McGregor is apparently accused of causing 'severe emotional distress, mental trauma and/or bodily harm.'
Chiesa is also going after the Barclays Centre, as he feels that security failed 'to engage in proper security measures to protect the plaintiff and other patrons.'
McGregor was arrested after the attack, but only ended up with community service despite being charged with criminal mischief and three counts of misdemeanour assault.
McGregor is now looking to prove his enemies wrong when he faces Nurmagomedov in his first UFC fight since 2016, with the Irishman yet to fight since his boxing defeat to Floyd Mayweather a year ago.
Chiesa's lawsuit could open the door for more actions against McGregor with UFC straw weight fighters Rose Namajunas and Karolina Kowalkiewicz also on the bus at the time of McGregor's attack.
Namajunas' coach Trevor Wittman told Ariel Helwani's MMA Show on ESPN that his fighter is still deeply traumatised by the events in New York.
'She doesn't leave her house,' Wittman said last week.
'It's still there. She doesn't go in public places. When you're in a public place and there's people everywhere, you're going to be like ‘Oh my god, what could happen?'
— This story originally appeared on thesun.co.uk