The 2011 season was the Kansas City Chiefs' 42nd in the National Football League (NFL), their 52nd overall and their third under the head coach/general manager tandem of Todd Haley and Scott Pioli.

A season-ending hand injury to their starting quarterback Matt Cassel in their eighth game of the season proved especially significant.

After starting the season 5–8, head coach Todd Haley was fired after a 37–10 loss to the New York Jets.

Haley was replaced by defensive coordinator Romeo Crennel on an interim basis for the remainder of the season.

One bright spot of the season is the first game after Crennel took over as interim head coach.

Hoping to snap a three-game losing streak, the Chiefs went home for a Week 12 Sunday night duel with the Pittsburgh Steelers.

Kansas City delivered the game's first punch in the opening quarter with a 41-yard field goal from kicker Ryan Succop.

The Steelers would answer in the second quarter with kicker Shaun Suisham getting a 21-yard field goal, followed by quarterback Ben Roethlisberger completing a 2-yard touchdown pass to tight end Weslye Saunders.

In one of the biggest upsets of the year, the Chiefs beat the heavily favored Green Bay Packers, ending their hopes of a perfect season.

The Chiefs defense held Packers quarterback Aaron Rodgers to 235 yards, a 49% completion percentage, and his only game of the season without multiple passing touchdowns in what was Rodgers' worst game statistically of the season.