By the end of his third season, Watt had established himself as one of the best pass-rushers in the NFL, tallying an AFC-high 14.5 sacks and a league-high eight forced fumbles. He was voted Team MVP by his teammates, being the first defensive player to win the award since Troy Polamalu in 2010. Watt was voted All-Pro as both edge rusher (1st Team) and linebacker (2nd Team). He was also nominated for the NFL Defensive Player of the Year award, finishing third in voting.. Following the season, Watt was ranked 25th by his fellow players on the NFL Top 100 Players of 2020.

Watt started his collegiate career as a tight end recruit for the Wisconsin Badgers. Watt’s knee was injured in the 2014 season and he was in the recovery process until the middle of the 2015 season. He did not play a game from October 2012 to September 2015.

In July 2015, Watt was asked by head coach Paul Chryst to switch to a defensive position as a redshirt sophomore. Badgers’ outside linebackers coach Tim Tibesar recalled Watt’s position change saying, “At that time, even though he was in his third fall at Wisconsin, it was kind of like having a freshman come in. You’re trying to teach him for the first time how to play outside ‘backer in our system.” After the fourth game of his junior season, he led the Big Ten conference in sacks. In the Michigan State game, he was named the Big Ten Player of the Week and was given the Walter Camp National Defensive Player of the Week Award.

During the 2016 season, Watt recorded 59 total tackles and 11.5 sacks. Additionally, he recorded an interception and a defensive touchdown during the Badgers’ game against Purdue. Watt also received first team All-American honors by Sports Illustrated and second team honors by The Associated Press for his play during the 2016 season. On November 29, 2016, Watt was named First Team All-Big Ten. On January 3, 2017, Watt announced on Twitter that he would forgo his senior season and enter the 2017 NFL Draft.

Born the youngest of three boys, Watt was raised by his parents, Connie and John Watt, in Pewaukee, Wisconsin. His father was a firefighter for 25 years and his mother is the vice president of an independent inspections company. His two older brothers, J.J. and Derek, both played at Wisconsin and are both currently playing in the NFL. Derek is a fullback for the Pittsburgh Steelers and was selected in the sixth round with the 198th overall pick in the 2016 NFL Draft. J.J. is a three-time NFL Defensive Player of the Year and five-time Pro Bowl defensive end for the Houston Texans and was selected in the first round with the 11th overall pick in the 2011 NFL Draft. T.J. was teammates with Derek at Wisconsin from 2012-2015. Also during his time at Wisconsin, Watt majored in retailing and consumer behavior.

The Pittsburgh Steelers selected Watt in the first round with the 30th overall pick in the 2017 NFL Draft. Watt was the fourth linebacker selected and the second outside linebacker. He was also the fourth linebacker taken in the first round by the Pittsburgh Steelers since 2013.

On June 14, 2017, the Pittsburgh Steelers signed Watt to a fully guaranteed, four-year, $9.25 million contract with a signing bonus of $4.87 million.

Watt made his professional regular season debut and first career start in the Pittsburgh Steelers’ season-opener against the Cleveland Browns on September 10, 2017, where he recorded seven combined tackles, two sacks, and one interception, which came off of quarterback DeShone Kizer, as the Steelers won by a score of 21–18. He recorded his first career sack, tackle, and interception during the game and returned the interception for 17-yards. He became the first rookie to start at linebacker for the Pittsburgh Steelers since Aaron Jones in 1988. The following week, he assisted on two tackles before leaving during the first half of the Steelers’ 26–9 victory over the Minnesota Vikings with a groin injury. He was declared out for Week 3 against the Chicago Bears. On October 22, 2017, Watt made six combined tackles and made his fourth sack of the season on Cincinnati Bengals’ quarterback Andy Dalton during the Steelers’ 29–14 victory. He tied Bud Dupree (2014) and LaMarr Woodley (2007) for the franchise record for most sacks by a rookie with his fourth. Watt finished his rookie season with 54 combined tackles (40 solo), seven pass deflections, seven sacks, and an interception in 15 games and 15 starts.

The Pittsburgh Steelers finished atop the AFC North with a 13-3 record and earned a playoff berth. On January 14, 2018, Watt started his first career playoff game and recorded two combined tackles and deflected a pass in the 45-42 loss to the Jacksonville Jaguars in the AFC Divisional Round.

Watt started in the Pittsburgh Steelers’ season-opener at the Cleveland Browns and recorded a season-high ten combined tackles (seven solo), three sacks, and blocked a potential game-winning field goal during overtime in a 21-21 tie. He earned AFC Defensive Player of the Week for his performance. On October 7, 2018, Watt recorded eight combined tackles, tied his season-high of three sacks, and forced a fumble in the Steelers’ 41-17 win against the Atlanta Falcons. His performance earned him his second AFC Defensive Player of the Week award of the year. He started in all 16 games in 2018 and recorded 68 combined tackles (50 solo), 13 sacks, six forced fumbles, and three pass deflections. He received an overall grade of 75.8 from Pro Football Focus in 2018, which ranked as the 24th highest grade among all qualifying edge defenders.. After the season, Watt was ranked #93 on the NFL Top 100 Players of 2019.

On March 17, 2020, the Steelers signed Watt’s older brother Derek, putting the two brothers on the same team. On April 28, 2020, the Steelers exercised the fifth-year option on Watt’s contract.

In Week 1 against the New York Giants, Watt recorded his first interception of the season off a pass thrown by Daniel Jones during the 26–16 win. In Week 2 against the Denver Broncos, Watt recorded his first 2.5 sacks of the season on Jeff Driskel during the 26–21 win. He was named the AFC Defensive Player of the Week for his performance in Week 2. On October 1, 2020, Watt was named the AFC Defensive Player of the Month for his performance in September. In Week 5, Watt’s 26th birthday, against the Philadelphia Eagles, he recorded one sack on Carson Wentz during the 38–29 win. In Week 8 against the Baltimore Ravens, Watt recorded a sack on Lamar Jackson and hit him a total of five times during the 28–24 win.