Hunt agreed to relocate the franchise to Kansas City on May 22, 1963 and on May 26 the team was renamed the Kansas City Chiefs. Hunt and head coach Hank Stram initially planned on retaining the Texans name, but a fan contest determined the new “Chiefs” name in honor of Mayor Bartle’s nickname that he acquired in his professional role as Scout Executive of the St. Joseph and Kansas City Boy Scout Councils and founder of the Scouting Society, the Tribe of Mic-O-Say. A total of 4,866 entries were received with 1,020 different names being suggested, including a total of 42 entrants who selected “Chiefs.” The two names that received the most popular votes were “Mules” and “Royals.”

The franchise became one of the strongest teams in the now thriving American Football League, with the most playoff appearances for an AFL team (tied with the Oakland Raiders), and the most AFL Championships (three). The team’s dominance helped Lamar Hunt become a central figure in negotiations with NFL Commissioner Pete Rozelle to agree on an AFL–NFL merger. In the meetings between the two leagues, a merged league championship game was agreed to be played in January 1967 following the conclusion of the leagues’ respective 1966 seasons. Hunt insisted on calling the game the “Super Bowl” after seeing his children playing with a popular toy at the time, a Super Ball. While the first few games were designated the “AFL–NFL World Championship Game,” the Super Bowl name became its officially licensed title in years to come.

Contrary to common belief, it was not the AFL, but the NFL that initiated discussions for a merger between the two leagues, as it was fearful that Davis’ “take no prisoners” tactics would seriously reduce its talent base. Tex Schramm, the general manager of the NFL’s Dallas Cowboys since 1960, secretly contacted AFL owners, led by Lamar Hunt of Kansas City, and asked if they were interested in a merger. The talks were conducted without the knowledge of Davis, the new AFL commissioner. On the evening of June 8, 1966, the collaborators announced a merger agreement in New York.

Following their championship win, the NFL-AFL merger placed the Chiefs in the newly created AFC West division with the Chargers, Raiders, and Broncos.

Super Bowl IV, the fourth AFL-NFL World Championship Game in professional American football, was played on January 11, 1970, at Tulane Stadium in New Orleans, Louisiana. The American Football League (AFL) champion Kansas City Chiefs defeated the National Football League (NFL) champion Minnesota Vikings by the score of 23–7. This victory by the AFL squared the Super Bowl series with the NFL at two games apiece. This was also the final AFL-NFL World Championship Game before the two leagues merged into one after the season.

In 1972, the Chiefs moved into the newly constructed Arrowhead Stadium at the Truman Sports Complex outside of Downtown Kansas City. The team’s first game at Arrowhead was against the St. Louis Cardinals, a game which the Chiefs won 24–14.

Arrowhead Stadium in Kansas City, Missouri, is home to the NFL’s Kansas City Chiefs. Part of the Truman Sports Complex, together with Kauffman Stadium, it is the 28th largest stadium in North America and fifth largest NFL stadium in seating capacity, behind AT&T Stadium, Lambeau Field, MetLife Stadium, and FedExField. It is the largest sports facility by capacity in the state of Missouri. A $375 million renovation was completed in 2010.

Lamar Hunt died December 13, 2006 at Presbyterian Hospital in Dallas of complications related to prostate cancer. The Chiefs honored their owner for the remainder of the season, as did the rest of the league. Upon his death his son Clark Hunt was named chairman of the Kansas City Chiefs.