Bills lead Chiefs at half time behind Allen's two rushing touchdowns
Josh Allen was strong for Buffalo, completing 14-of-19 passes for 111 yards and adding 51 yards and two touchdowns on the ground on eight carries.
Buffalo took the lead on a strong drive as time ticked down in the second half, which was capped off by Allen's second rushing touchdown of the game from five yards out with under 30 seconds remaining.
Midway through the second quarter, the Chiefs took their first lead of the game on a communication breakdown by the Bills defence. Kelce was left uncovered for a 22-yard touchdown to give Kansas City a 13-10 lead.
The back-and-forth affair continued into the second quarter, as Mahomes drove Kansas City downfield but missed a throw on third down and had to settle for a 29-yard field goal by Harrison Butker.
The rushing attack was dominant for Buffalo on their second drive, as they controlled the ball for over eight minutes before Allen punched in a rushing touchdown from five yards out. They rumbled for 55 rush yards on the drive.
Early in the second quarter, the plays count was 24-6 for the Bills as they thoroughly controlled possession.
Mahomes and the Chiefs took their opening possession down the field but Mahomes' third-down pass was batted away by Dane Jackson, forcing Butker to hit a 47-yard field goal.
The winner of the game will travel to Baltimore to take on the Ravens with a spot in the Super Bowl on the line.