[5][6][7][8] Reid began his professional coaching career with the Green Bay Packers, serving as an offensive assistant from 1992 to 1998 and was a member of the team that won Super Bowl XXXI.

Reid led the Eagles to nine playoff runs, six division titles, five NFC Championship Games (including four consecutive from 2001 to 2004), and an appearance in Super Bowl XXXIX.

Reid first grew his mustache while sailing as a cadet aboard the TS Golden Bear during his time at the California Maritime Academy.

In 1971, at age 13, Reid was on Monday Night Football participating in the Punt, Pass, and Kick competition;[11] he was already so large that he wore the jersey of Les Josephson, who was 6 feet 1 inch (1.85 m) and 207 pounds (94 kg).

[15][20] In 1995, he became the assistant offensive line and tight ends coach, where he helped lead the 1996 team to a Super Bowl XXXI win over the New England Patriots.

[21][22][23] Reid was named the Packers' quarterbacks coach in 1997, replacing Marty Mornhinweg, who left to be the offensive coordinator for his predecessor in Green Bay, Steve Mariucci.

[21] Consistent with his reputation for a focus on football details, Reid arrived at his interview with the Eagles with a five-inch thick book he developed on how he would go about running the team if given the job.

[13][25] Some in the Philadelphia news media criticized the hiring, citing the availability of other candidates who had already served previously as successful head coaches.

[27][28] In 2000, the Eagles posted an 11–5 regular-season record and won their first playoff game since the 1995 season, beating the Tampa Bay Buccaneers in Philadelphia on New Year's Eve.

[29][30] In 2001, Reid was named executive vice president of football operations of the Eagles, effectively making him the team's general manager.

After three straight NFC Championship losses, the team beat the Atlanta Falcons by a score of 27–10 and made it to Super Bowl XXXIX but fell to the New England Patriots 24–21.

[37] A couple of weeks later quarterback Donovan McNabb suffered a season-ending injury, leaving the Eagles without the services of two of their star players.

The season appeared to be lost by October with another season-ending injury to McNabb, turning a 4–1 start into a mid-season breakdown which left the team 5–5.

[43] Reid coached backup quarterback, Jeff Garcia, and the 5–6 Eagles, to victories over a slew of NFC rivals including the Carolina Panthers, Washington Redskins, New York Giants, and Dallas Cowboys.

[46] In the 2008 season, Reid's 9–6–1 Eagles managed to defeat the defending Super Bowl Champion New York Giants in the divisional round, leading the team to a fifth NFC Championship game under his tenure, where they lost to the Arizona Cardinals by a score of 32–25.

[51] In the 2009 season, Reid failed to win a first-round post-season game for the first time in his career, with his 11–5 Eagles being eliminated by the first place Dallas Cowboys by a score of 34–14 in the Wild Card Round.

On December 31, 2012, the day after the season ended with a 42–7 loss to the New York Giants, Eagles owner Jeffrey Lurie announced that Reid's contract would not be renewed.

[63] Lurie said that Reid's induction into the Philadelphia Eagles Hall of Fame was inevitable, and players gave their former coach a standing ovation during his last meeting with them.

[68] A week later, however, the Chiefs hired John Dorsey, who had previously worked with Reid as an assistant in Green Bay, as general manager.

[79] Reid would go on to lead the Chiefs to their first playoff win since the 1993 season in a 30–0 shutout of the Houston Texans,[80] but the team was defeated 27–20 in the Divisional Round against the New England Patriots.

[87][88] After their strong start, the Chiefs lost six of their next seven games, resulting in Reid conceding play calling duties to offensive coordinator Matt Nagy.

The Chiefs won their last four games to finish 10–6 and clinch the AFC West for a second consecutive year, the first back-to-back division titles in franchise history.

[89] The team ultimately suffered a sixth consecutive home playoff loss in a 22–21 defeat against the Tennessee Titans in the Wild Card Round.

Despite holding a 21–3 lead at halftime, the Chiefs were shut out during the second half as the Titans scored 19 unanswered points to win the game.

[92] With the victory, the Chiefs hosted the AFC Championship for the first time in franchise history, which they lost 37–31 to the eventual Super Bowl LIII champion New England Patriots in overtime.

[100] The Chiefs went on to defeat the San Francisco 49ers 31–20, earning the franchise their first Super Bowl victory in 50 years and Reid's first as a head coach.

[4] The Chiefs lost the game 27–24 to the Cincinnati Bengals in overtime after surrendering a 21–3 lead, which was tied with the 2006 Indianapolis Colts' comeback against the New England Patriots as the largest in a conference championship.

[112][113] The Chiefs defeated the Jacksonville Jaguars in the Divisional Round and the Cincinnati Bengals in the AFC Championship to make the Super Bowl for the 3rd time in four seasons.

[126] Reid led the Chiefs to their third consecutive Super Bowl appearance following wins over the Houston Texans in the Divisional Round and the Buffalo Bills in the AFC Championship.

[149][150] Britt, his second son, served as an assistant coach under his father until 2021 when he was suspended and not offered a new contract after he was involved in a DWI car accident causing severe injuries to a five-year-old girl.