As the head coach of the Giants, Parcells took over a franchise that had qualified for the playoffs only once in the past decade and had only one winning record in their last 10 seasons.

He left the Patriots after their Super Bowl loss and became the head coach and general manager of the Jets, who went from a one-win season to appearing in the AFC Championship Game by his second year.

Following his final retirement from coaching, Parcells served as the vice president of football operations for the Miami Dolphins from 2008 to 2010.

At 6 feet 2 inches (1.88 m) upon entering River Dell, he was large for his age, which enabled him to become a standout player on his high school's football, baseball, and basketball teams.

His basketball coach at River Dell was Mickey Corcoran, whom Parcells considers to be "next to my father ... the most important influence in my life.

Parcells, showing the kind of preparation that would make him a successful coach later, frequently arrived early to training sessions, in order to set up a radio.

[7] Feeling dissatisfied with his life away from football, Parcells returned to the sport in 1980 as the linebackers coach of the New England Patriots under Ron Erhardt.

Parcells, whose stifling 3–4 defense (known as the Big Blue Wrecking Crew) led by Lawrence Taylor, Carl Banks, Harry Carson, and Leonard Marshall, and an offense under the direction of Phil Simms, knocked off the San Francisco 49ers 49–3, and the Washington Redskins 17–0, in the playoffs before routing the Denver Broncos 39–20 in Super Bowl XXI.

While there are some claims that Chicago Bears coach Mike Ditka had been doused a year earlier,[22] NFL Films president Steve Sabol has stated that he can find no evidence to support it in any footage he has reviewed and that he believes the tradition started with Parcells and Jim Burt.

[23] Following the Super Bowl win, Parcells was courted by the Atlanta Falcons to become the head coach and general manager of the franchise.

Playing with a back-up quarterback in Jeff Hostetler and a 33-year-old veteran running back in Ottis Anderson, the Giants convincingly defeated the Chicago Bears in the divisional playoff, 31–3.

They followed that up with a dramatic, come-from-behind fashion over San Francisco, 15–13, in the NFC Championship game on a last-second 42-yard field goal by Matt Bahr, set up by a Roger Craig fumble caused by nose tackle Erik Howard.

Super Bowl XXV proved equally exciting as the Giants used tough defense and a ball-control and power-running Erhardt – Perkins style offense to stop the Buffalo Bills, 20–19, whose own last-second 47-yard field goal attempt by Scott Norwood missed wide right.

After a two-year hiatus, Parcells returned to the NFL in 1993 as the head coach for the struggling New England Patriots, who were fresh off of a 2–14 record in 1992.

Parcells had effectively been the team's general manager since arriving in New England, but felt Kraft would not allow him enough input in player personnel decisions.

[31] The New York Jets sought Parcells as head coach and general manager after a 4–28 record under Rich Kotite.

Jets owner Leon Hess gave Parcells complete control over football operations, the main sticking point in his dispute with Kraft.

However, quarterback Vinny Testaverde ruptured his Achilles tendon in the Jets' home opener against the New England Patriots and the season went downhill from there.

Following three straight 5–11 seasons, Dallas Cowboys owner Jerry Jones lured Parcells out of retirement and made him the head coach in 2003.

"[36] Jones enthusiastically embraced the idea, and supported Parcells' decision to have Cowboys equipment managers remove all of the star logos from rookie helmets.

Since then, all drafted and UFA (undrafted free agent) rookies that report to the Cowboys must officially make the roster before having the star logo permanently placed on their helmet.

Starting quarterback Quincy Carter was terminated for alleged drug use in favor of 40-year-old veteran Vinny Testaverde, who had been brought to the Cowboys from the New York Jets by his former coach in the off-season.

The Cowboys improved their defense before the 2005 season with the additions of first-round draft picks DeMarcus Ware and Marcus Spears.

Jerry Jones also added a number of high-priced older veteran players, acquiring nose tackle Jason Ferguson and cornerback Anthony Henry via free agency, and linebacker Scott Fujita via the Kansas City Chiefs.

On offense, the Cowboys felt the need to upgrade their passing game to complement their top 2004 draft pick, running back Julius Jones, and acquired quarterback Drew Bledsoe via free agency.

They were able to clinch a playoff berth as the 5th seed in the NFC, eventually losing 21–20 against the Seahawks in Seattle on January 6, on a botched hold by Tony Romo during a field goal attempt.

[43] Just a day prior, reports linking Parcells to the Atlanta Falcons' position of vice president of football operations were leaked.

[47] They finished with a 10-game improvement from the previous season, making the Dolphins one of two teams in NFL history to accomplish a 10-game turnaround, the other being the 1999 Indianapolis Colts.

[49] However, on March 6, 2014, Pro Football Hall of Fame executive Gil Brandt reported Parcells had met with Browns owner Jimmy Haslam as a courtesy consultant.

[50] In an interview with The Plain Dealer, Jimmy Haslam squashed any rumor that Parcells would be joining the front office, saying, "...Bill's not going to come work for us, okay?