Regular-season play was held from September 4, 2003, to December 28, 2003. Due to damage caused by the Cedar Fire, Qualcomm Stadium was used as an emergency shelter, and thus the Miami–San Diego regular-season match on October 27 was instead played at Sun Devil Stadium, the home field of the Arizona Cardinals. This was the first season in NFL history where every team won at least 4 games.
If an onside kick inside the final five minutes of the game does not go 10 yards, goes out of bounds, or is touched illegally, the receiving team will have the option of accepting the penalty and getting the ball immediately. Previously, the kicking team was penalized, but had another chance to kick again from five yards back.
League officials encouraged networks to immediately cut to a commercial break if an instant replay challenge review was initiated. Previously networks were generally not permitted to utilize those game stoppages for their prescribed commercial periods.
David Woodley: Having played for the Miami Dolphins in Super Bowl XVII, Woodley died from complications due to kidney and liver failure on May 4, 2003. Twenty years after Super Bowl XVII, he became the youngest Super Bowl starting quarterback to die, until the death of Super Bowl XXXIV starter Steve McNair at age 36 in 2009. Woodley was buried at St. Joseph Cemetery in Shreveport, alongside his parents.
Within each conference, the four division winners and the two wild card teams (the top two non-division winners with the best overall regular season records) qualified for the playoffs. The four division winners are seeded 1 through 4 based on their overall won-lost-tied record, and the wild card teams are seeded 5 and 6. The NFL does not use a fixed bracket playoff system, and there are no restrictions regarding teams from the same division matching up in any round. In the first round, dubbed the wild-card playoffs or wild-card weekend, the third-seeded division winner hosts the sixth seed wild card, and the fourth seed hosts the fifth. The 1 and 2 seeds from each conference then receive a bye in the first round. In the second round, the divisional playoffs, the number 1 seed hosts the worst surviving seed from the first round (seed 4, 5, or 6), while the number 2 seed will play the other team (seed 3, 4, or 5). The two surviving teams from each conference's divisional playoff games then meet in the respective AFC and NFC Conference Championship games, hosted by the higher seed. Although the Super Bowl, the fourth and final round of the playoffs, is played at a neutral site, the designated home team is based on an annual rotation by conference.
The Atlanta Falcons unveiled a new uniform design featuring red trim down the sides of both the jerseys and pants. The pants were switched from gray to white, and black pants were also introduced for selected games. Black remained the primary jersey color while a red alternate jersey was also introduced. The falcons helmet logo was redesigned to be more aggressive and closely resemble a capital "F".
The Cincinnati Bengals added new alternate black pants with their black jerseys for select home games.
The New Orleans Saints wore gold pants full time, discontinuing using black pants with their white jerseys.
The Philadelphia Eagles added silver trim to the jersey numbers on uniforms, and black third alternate uniforms.
The San Diego Chargers wore white pants instead of blue with their white jerseys. They wore blue pants with their blue jerseys for the game vs. the Dolphins which had to be moved from San Diego to Arizona due to wildfires in southern California.