The Chiefs clinched a playoff berth, but lost to the Indianapolis Colts in the Wild Card round of the playoffs by a score of 45–44, after blowing a 38–10 second half lead, extending an 8-game playoff losing streak dating back to the 1993 season, which was the worst in NFL history.
The Chiefs started their 2013 season on the road against the Jaguars. The Jags scored a safety when J.T. Thomas blocked a punt in the end zone giving them a 2-0 lead. The Chiefs took the lead as Alex Smith found Donnie Avery on a 5-yard touchdown pass for a 7-2 lead. This was followed up by Smith finding Junior Hemingway on a 3-yard pass sending the game to a 14-2 game. In the 2nd quarter, the Chiefs continued to dominate as Jamaal Charles ran for a 2-yard touchdown giving the team a 21-2 halftime lead.
After a scoreless 3rd quarter, the Chiefs scored the only points of the 2nd half in the 4th quarter when Tamba Hail returned an interception 10 yards for a touchdown.
The Chiefs beat the Jacksonville Jaguars 28–2, the first time in NFL history a game ended with that score. It was also the first time in 20 years a team scored 2 points during a regular season game. The Jaguars crossed the 50 yard line once but failed to score. The Jaguars only score came when a blocked punt that went out of the end zone.
The Chiefs made their regular season debut at home against the Cowboys. They would score first as Jamaal Charles caught a 2-yard touchdown pass from Alex Smith for a 7-0 lead. The Boys got on the board as Dan Bailey kicked a 51-yard field goal for a 7-3 game followed up by Tony Romo and Dez Bryant hooking up on a 2-yard pass for a 10-7 lead. With the 2nd quarter being scoreless, the Boys gradually held on to the lead.
In the 3rd quarter, Bailey nailed a 30-yard field goal to increase their lead 13-7. However, the Chiefs retook the lead as Smith found Dwayne Bowe on a 12-yard pass making the score 14-13. In the 4th quarter, the Chiefs increased their lead as Ryan Succop nailed a 40-yard field goal for a 17-13 lead. The Boys then tried to rally late, but came up a point short when Bailey kicked a 53-yard field goal as the Chiefs won the game 17-16 sending them to their first 2-0 start since 2010.
After a close call win at home, the Chiefs traveled to Philadelphia to take on the Eagles in a TNF duel. The Chiefs started their scoring when Ryan Succop kicked a 33-yard field goal for a 3-0 lead. This was followed by Eric Berry returning an interception 38 yards for a touchdown for a 10-0 lead. The Eagles managed to get on the board later on in the quarter when Michael Vick found Jason Avant on a 22-yard touchdown pass (with a failed PAT) making the score 10-6. The Chiefs continued to dominate as Succop kicked 2 field goals increasing his teams lead from 7 to eventually 10 points with field goals from 31 and 34 yards out 13-6 and 16-6 at halftime. In the 3rd quarter, the Eagles managed to rally coming within 7 points as Alex Henery kicked a 29-yard field goal for the only score of the quarter. The Chiefs pulled away as Jamaal Charles ran for a 3-yard touchdown for a 23-9 lead. The Eagles then would fire back as LeSean McCoy ran for a touchdown from 41-yards out once again coming within 7 23-16. With Succop's 38-yard field goal, the Chiefs were able to seal the game with a final score of 26-16 sending them to a 3-0 start, their first such start since 2010.
After a win over the Eagles, the Chiefs returned home for a game against the Giants. After a scoreless 1st quarter, they got on the board as Alex Smith found Sean McGrath on a 5-yard pass for a 7-0 lead. The Giants managed to tie the game up as Eli Manning found Victor Cruz on a 69-yard pass making the score 7-7. Ryan Succop then kicked a 51-yard field goal to send the Chiefs to a 10-7 halftime lead.
In the 2nd half, the Chiefs dominated as Dexter McCluster would run a punt back 89 yards for a touchdown increasing their lead to 17-7 for the only score of the 3rd quarter. In the 4th quarter, Alex Smith threw 2 more touchdown passes to Jamaal Charles and Dwayne Bowe from 2 and 34 yards out that would eventually seal the game for them moving them up 24-7 before the final score sat at 31-7.
The win sent the Chiefs to their first 4-0 start since 2003.
The Chiefs improved to 6–0 after defeating the Oakland Raiders 24–7, and snapped a 6-game home losing streak to the Oakland Raiders dating back to the 2007 season. It was at this game that Arrowhead Stadium fans set a new Guinness World Record for loudest outdoor stadium in any sport.
It also featured the largest flyover with 42 planes.
With the win, the Chiefs improved to 7-0 for the first time they would start a season with such a record since 2003. With the Broncos' loss to the Colts, they became the league's only undefeated team while they also became leader of the AFC West.
San Diego triumphed in the highest-scoring matchup with Kansas City since a 42-41 loss in 1986. The game lead changed eight times as Alex Smith threw for 294 yards and three touchdowns, but Rivers (392 yards) won it in the final seconds on a 26-yard score to Seyi Ajirotutu. The loss was Kansas City's second straight after the Chiefs' nine-game winning streak.
Kansas City would lead 21-7 at one point, but the Broncos would come back to win 35-28 and sweep the Chiefs for the second straight season. With their third straight loss, the Chiefs fell to 9-3. They were the first 9-0 team in NFL history to lose 3 straight games following a 9-0 start.
With no Alex Smith playing due to Kansas City resting their starters for the playoffs, it was up to Chase Daniel to guide the Chiefs. Kansas City missed a field goal at the end of regulation. The Chargers would win in overtime on a field goal. With the loss, the Chiefs finished the regular season 11-5 and finished 2-4 against their division and 9-1 against the rest of the NFL.