No cause of death was announced.
"Rest in Peace Chris," tweeted agent Drew Rosenhaus. "Condolences to all his family, friends and loved ones. We will miss you."
Smith had made five tackles in five games this season for the Seattle Sea Dragons of the XFL, a league for players hopeful of attracting the attention of NFL scouts.
"Rest in Peace to a West Rowan Legend!" tweeted West Rowan High School in North Carolina. "Chris was a better person than he was player! The impact he had on those around him will be remembered forever!"
Smith made 80 tackles, 11 of them sacks, and forced three fumbles in his NFL career from 2014 to 2021 with the Jacksonville Jaguars, Cincinnati Bengals, Cleveland Browns, Las Vegas Raiders and Houston Texans.
"We are deeply saddened by the passing of former Browns defensive end Chris Smith," the Browns said in a statement.
"Chris was one of the kindest people, teammates and friends we've had in our organization. Our thoughts and prayers are with his family during this difficult time."
