Pictures from the awards appeared to show McGregor (33) and the 31-year-old rapper being kept apart by security after they apparently had a scuffle on the red carpet.
The former UFC champion attended the ceremony at the Barclays Centre in New York with his partner Dee Devlin while the US musician arrived with his Hollywood actress girlfriend Megan Fox.
Despite footage circulated online McGregor said "absolutely nothing happened" between him and MGK as he dismissed the incident as a rumour and claimed he had no clue who MGK was.
Speaking to Entertainment Tonight, Dublin-born McGregor said “nothing” happened.
He said: “Absolutely nothing. I don’t know. He showed up, and I don’t know. I don’t know the guy.
“Nothing happened with me, I only fight real fighters, people that actually fight, you know what I mean
“I certainly don’t fight little vanilla boy rappers. I don’t even know the guy. I don’t know anything about him, except that he’s with Megan Fox.”
However, Jake Paul who has goaded McGregor in the past, said he heard the Irishman mistook MGK for him.
Paul, who is friends with MGK, slammed McGregor for his "disrespectful" behaviour.
"It's hilarious,” Paul said. “Some people are saying that Conor McGregor mistook him for me because we look the same, like blonde hair, little bit tall. That was like the rumour that happened. I think it's hilarious.
“Conor McGregor is a real fighter. Why is he on a celebrity red carpet throwing drinks at Megan Fox and Machine Gun Kelly? It's just disrespectful.
"But Kells (MGK) handled himself like a professional, he didn't get hot, he didn't retaliate because I think he knows that Conor just looked like an idiot. This guy is falling apart and trying to find any reason to get attention."
The YouTube star also joked that McGregor's altercation with MGK was his "tactic" to win fights outside the octagon since he has lost two consecutive fights inside one.
A big combat sports fan, MGK attended McGregor's trilogy bout with Poirier in July at the T-Mobile Arena in Las Vegas.
And he is close with Paul, as well as his brother Logan, making an appearance at their after-party following the elder sibling's exhibition bout with Floyd Mayweather earlier this year.
McGregor's spokespeople have denied a claim that the issue began with Machine Gun Kelly, whose real name is Colson Baker, refusing to take a picture with the Irishman.
And when asked about the alleged altercation MGK simply walked away without answering the question.
After Paul won a split decision against Tyron Woodley in Cleveland last month, Paul addressed the prospect of a match with McGregor.
“To be honest, no way he hits harder than Woodley,” he cleared. “He doesn’t weigh as much as Woodley. He’s shorter than Woodley. I’ve said it before the fight, I think Woodley is a harder fight than him, especially the way he’s going. Conor is going down, I’m going up. Woodley came in game, we’ll see.”