The Northern Irishman was in Denver for the BMW Championship where he finished tied for eighth, and he was a special guest for the Broncos opening game of the new NFL season on Sunday night.
The Broncos beat the Colts 31-24 as quarterback Peyton Manning threw for 269 yards and three touchdowns against his former team in the win that saw the five-time MVP become just the second quarterback to beat all 32 teams in the NFL.
McIlroy signed autographs pitchside before kick-off in Denver, and met the veteran in the Denver locker room after the game.
McIlroy fell to fourth place in the FedEx Cup standings after this weekend's tournament in Denver, as a disappointing four-putt on Saturday didn't help his cause.
He managed to take his mind off of the result however by watching one of the greatest quarterbacks in the history of the NFL throw three first-half touchdowns to tight-end Julius Thomas.
The Colts made a comeback in the second-half but the Broncos held on the win their opening game of the new campaign to get off to the perfect start.
Will the Denver Broncos win the Super Bowl this season?