Former NFL star Jason Kelce has apologised for smashing the phone of a person who directed an alleged homophobic slur at his brother, Kansas City player Travis Kelce.

Footage emerged of Jason Kelce making his way through a group of college football fans over the weekend when it's claimed one referenced Travis Kelce's relationship with pop star Taylor Swift.

The person, wearing a Penn State hoodie, allegedly used a homophobic slur, after which Jason Kelce took the phone from his hand and hurled it to the ground.

Footage from after the incident showed Kelce, part of ESPN's broadcast of the Penn State-Ohio State game, getting back up and shouting in the owner's face: "Who's the f****t now?"

Kelce apologised for his behaviour on ESPN's coverage before the Chiefs' Monday night (local time) NFL game against Tampa Bay in Kansas City.

"I'm not happy with anything that took place. I'm not proud of it," he said.

"I really don't. I don't think it leads to discourse and it's the right way to go about things.

"At that moment I fell down to a level I shouldn't have. The bottom line is, I try to live my life by the golden rule [do unto others] — that's what I've always been taught.

"I try to treat people with common decency and respect and I'm going to keep doing that moving forward, even though I fell short this week."

Penn State University Police are reportedly investigating the incident.

Kelce played 13 seasons in the NFL with the Philadelphia Eagles.

Kelce — who played centre, one of the least glamorous positions in American football — has seen his profile away from the game rise since brother Travis and Swift started dating.

The brothers faced off in the Super Bowl in 2023 and the pair host the New Heights podcast together, which has exploded in popularity in the past year.