He was the head coach of the Carolina Panthers (2002–2010), Denver Broncos (2011–2014) and Chicago Bears (2015–2017) of the National Football League (NFL).

Fox attended Castle Park High School in Chula Vista, California, where he played football under local celebrated coaches Gil Warren and Reldon "Bing" Dawson.

Fox received a bachelor's degree in physical education and earned teaching credentials from San Diego State.

[4] Sid Gillman, past head coach of the San Diego Chargers, was the athletic director at the time.

In 1980, Fox was the defensive backs coach for the Boise State University Broncos when they won the NCAA Division I-AA Football Championship.

[7] Fox was the defensive coordinator for the Los Angeles Raiders[8] and later that of the New York Giants during Super Bowl XXXV, which they lost.

In the 2003 season Fox led the Panthers to Super Bowl XXXVIII, losing 32–29 to the New England Patriots on a last-second field goal by Adam Vinatieri.

[19] Tom Moore, currently an offensive consultant for the Tampa Bay Buccaneers, is still active in the league but works from home.

On December 31, 2010, Carolina Panthers owner Jerry Richardson announced that he would not be renewing Fox's contract at the conclusion of the 2010 season.

In week 17 of the 2012 season, Fox won his 100th career game as an NFL head coach, including the playoffs, beating the Kansas City Chiefs 38–3.

[27] Fox, while playing golf in North Carolina near his offseason home in Charlotte during the Broncos bye week, reported feeling dizzy and was taken for examination to the hospital, where doctors told him not to put off valve replacement surgery any longer; he had done so earlier in the year to continue coaching this season.

Hosting Peyton Manning's former team, the Indianapolis Colts at home in the Divisional Round, the Broncos were upset 24–13 and were eliminated from the playoffs.

[33] On January 12, 2015, the day after Denver lost in the Divisional Round of the playoffs, Fox and the Broncos mutually agreed to part ways.

However, general manager John Elway felt the Broncos hadn't shown enough fight at critical times in the playoffs.

[40] On March 27, 2022, it was announced that Fox was hired by the Indianapolis Colts to be their senior defensive assistant under head coach Frank Reich.