Langer was a 6'2" linebacker and an honorary All-American with the class of 1969 South Dakota State University Jackrabbits. After going undrafted, he signed a free agent contract with the Cleveland Browns but did not stick with the team through training camp. He signed another free agent contract to play with the Dolphins, appearing sparingly (in six games) during his rookie season. He wore the number 62 jersey through his Miami career.
In 1971, Langer again appeared off the bench for Miami, earning playing time in all 14 of Miami's games. Miami went 10-3-1 that season, earning their first ever Super Bowl appearance, losing to the Dallas Cowboys, 24-3 in Super Bowl VI.
Langer joined the starting lineup for the first time in 1972, starting every Miami game at center. Miami's rushing offense was far and away the NFL's best, leading the league with 613 runs for 2,960 yards and 26 touchdowns. Miami also led the NFL with 385 points scored and 5,036 total yards gained. Miami's above average pass protection helped the Dolphin's quarterback tandem of Bob Griese and Earl Morrall earn an NFL best 86.9 passer rating. Miami finished the season 17-0 after dispatching the favored Washington Redskins, 14-7 in Super Bowl VII.
Langer was named to his first Pro Bowl roster (one of 12 Dolphins) as well as the All-NFL team (one of 13 Dolphins), starting every game in 1973. Miami's 343 points scored was the fifth best total in the NFL. Boasting the best defense in the NFL, the offense was efficient, running an NFL low 776 plays, and gaining an NFL high 5.3 yards per play. They also allowed an NFL low 13 sacks. Miami ran down the opposition, winning their second Super Bowl in a row, 24-7 over the Minnesota Vikings.
In 1974, Langer started every game at center, one of 10 Dolphins invited to the Pro Bowl. He also made his second consecutive All-NFL First Team (one of eight Dolphins). Miami posted an 11-3 record, winning the AFC East. Miami led the NFL with 25 rushing touchdowns scored.
1975 would see Langer earn his third consecutive slot on both the Pro Bowl (one of three from Miami) and the All-NFL first team (one of four Dolphins). Miami posted an AFC East lead tying 10-4 record, but did not make a playoff appearance for the first time since the AFL/NFL merger. Miami rushed for an NFL fourth best 2,500 ground yards, along with 26 touchdowns on the season.
1976 would see Miami post their first losing record since 1969, at 6-8. Langer started every game at center, making his fourth consecutive Pro Bowl appearance (the only Dolphin on the team). Miami's offense graded out in the middle of the NFL in every major trackable category.
In 1977, Langer again started every Dolphin's game at center. He was chosen to represent Miami at the Pro Bowl for the fifth time in a row (one of five Miami players), as well as returning to the All-NFL first team (one of six Dolphins). Miami posted an AFC third best 10-4 record, but nonetheless missed the playoffs. Miami's 22 passing touchdowns (on an NFL best 7.1 touchdown percentage) ranked second in the NFL.
1978 would see Langer continue to represent Miami at the postseason Pro Bowl (one of five Dolphins), his sixth consecutive trip. Miami returned to the postseason with a wildcard berth clinching 11-5 record. Miami led the AFC with 372 points scored and a passer rating of 82.9 on the season.
In 1979, Langer started the first nine games of the season at center, bringing his consecutive starts streak to 141 before suffering a knee injury, which sidelined him for the rest of the campaign. He never rejoined the Dolphins, instead appearing with the Minnesota Vikings sparingly over the next two seasons.
Langer is recognized as one of the NFL's best ever centers. He represents Miami at the Pro Football Hall of Fame, Class of 1987. Annually, the Jim Langer Award is presented to the top Division II Offensive Lineman in the country.