Anthony Cliff, of Las Vegas, alleges in the suit that the bodyguards beat him after American Mayweather gave the "thumbs down" sign when Cliff asked a question about the much-anticipated showdown with Filipino superstar Manny Pacquiao.
Cliff claims in the suit that he was attacked near the valet stand at the Palms Casino Resort in March of last year.
According to the suit, Mayweather's bodyguards struck Cliff in the face, slamming his head into the ground. They then kicked him several times in his back and side, the lawsuit says.
Las Vegas police said they investigated, after receiving a complaint, but no charges were laid, partly due to a lack of witnesses.
"At the end of the day there needs to be justice," said Afshin Tadayon, Cliff's lawyer. "You can't have people out there who do this sort of thing."
Cliff says he first spotted the boxer inside the casino and tried to take his photo but was rebuffed by a bodyguard.
Cliff then ran into Mayweather, who is 41-0 in his career, again outside and asked about a potential mega fight with Pacquiao.
The suit said Mayweather talked about Cliff being disrespectful and then gave his bodyguards the "thumbs down" signal which is the green light for them to attack.
"Not only does Mr. Cliff want to see a fight against Mr. Pacquiao, but so do many boxing fans," Tadayon said. "So, it was just a question."
Pacquiao and Mayweather have come close to reaching a deal for one of the most lucrative fights in boxing history but negotiations so far have hit a snag.
The latest suit adds to the list of Mayweather's court woes.
He failed to turn up for a court-ordered deposition in Las Vegas earlier this month in a federal lawsuit alleging he defamed Pacquiao. Mayweather also faces charges from a domestic dispute.
Mayweather is scheduled to be in Los Angeles Wednesday for a news conference promoting his September 17 comeback fight against Victor Ortiz.