From the beginning, Dorsett and head coach Tom Landry had differing opinions on how he should run the ball. Landry initially designed precise running plays, but was eventually convinced that Dorsett was a different type of running back and instructed the offensive line to block and hold their man, while Dorsett chose the running lane with his gifted vision and instincts. In 1977, Dorsett's rookie year, he provided an instant impact, rushing for 1,007 yards (including a 206-yard rushing effort against the Philadelphia Eagles scoring 12 touchdowns and earning rookie of the year honors. He set a new Cowboys rookie record and was also the only Cowboy to rush for more than 1,000 yards in his rookie season. He held the record for 39 years, until 2016, when Ezekiel Elliott surpassed 1,000 yards in his 9th game and broke Dorsett's record in game 10 with 1,102 yards.
He was named the starter in the tenth game of the season, and became the first player to win the college football championship, then win the Super Bowl the next year, when the Cowboys beat the Denver Broncos 27–10 in Super Bowl XII. In his second season, Dorsett recorded 1,325 yards and 9 touchdowns, with the Cowboys once again reaching the Super Bowl although they lost 35–31 to the Pittsburgh Steelers in Super Bowl XIII.
In 1980, he had one of his best runs. With the ball on the four-yard line against the St. Louis Cardinals, , the right defensive end and linebacker had penetration, while the two cornerbacks were blitzing. Dorsett suddenly pivoted on his right foot, turned 360 degrees and ran wide around the left side, beating the safety and eluding a total of five defenders for a touchdown without being touched.
His most productive season was in 1981, when he recorded 1,646 yards, breaking the Cowboys franchise record.
Dorsett was elected to both the Pro Football Hall of and the College Football Hall of Fame in 1994 and was enshrined in the Texas Stadium Ring of Honor the same year. In 1999, he was ranked number 53 on The Sporting News’ of the 100 Greatest Football Players. He is the first of only two players in history (along with former running back Marcus Allen) who has won the Heisman Trophy, won the Super Bowl, won the College National Championship, been enshrined in the College Hall of Fame, and been enshrined in the Pro Football Hall Of Fame.