Tomlin spent the 1996 season as a graduate assistant at the University of Memphis, where he worked with the defensive backs and special teams.

[3] Tomlin was retained under new head coach Jon Gruden, and in 2002 and 2005, the Buccaneers led the NFL in total defense (fewest yards allowed per game).

[8] After spending 2006 as the Vikings' defensive coordinator, Tomlin was selected to interview for the vacant head coaching position with the 2005 Super Bowl champion Pittsburgh Steelers.

The others were Cowher (age 34 in 1992), Chuck Noll (38 in 1969), Bill Austin (38 in 1966), John Michelosen (32 in 1948), Jim Leonard (35 in 1945), Aldo Donelli (33 in 1941), Walt Kiesling (35 in 1939), Johnny "Blood" McNally (33 in 1937), and Joe Bach (34 in 1935).

Tomlin began his career with a 15–7 record in regular season play—as did his predecessor Cowher and all-time win-leader Don Shula.

[14] When the Steelers defeated the Baltimore Ravens in the 2008 AFC Championship Game,[15] Tomlin became the youngest NFL head coach to lead his team to a Super Bowl.

[18] The previous record was held by Jon Gruden, who was 39 when he won Super Bowl XXXVII with the Tampa Bay Buccaneers.

Coincidentally, Tomlin was the defensive backs coach under Gruden when the Buccaneers won the Super Bowl and was a key component in their success that year.

Facing the Baltimore Ravens on November 28, 2013, in a primetime Thanksgiving Day game with major playoff implications, Tomlin became the subject of controversy when video replay showed him interfering with a kick return.

With the Steelers trailing 13–7 in the third quarter, Tomlin stood just off the field along the visiting team's sideline as Baltimore's Jacoby Jones broke free on a kickoff return for a potential game-breaking touchdown.

[29] Tomlin, with his back to the approaching play, appeared to glance over his shoulder then place his foot briefly onto the field as he jumped out of the way, causing Jones to veer inside where he was tackled.

Following the game, Tomlin defended himself, stating he had simply wandered too close to the field while watching the play on the stadium's Jumbotron, a mistake he said coaches often make.

[29] On December 4, 2013, the NFL announced that they had fined Tomlin $100,000, and hinted it was considering stripping the Steelers of one or more draft picks because his actions affected the play on the field.

[35] The 2014 season saw the birth of the Killer B's era in which Roethlisberger along with wide receiver Antonio Brown and running back Le'veon Bell all hit their primes.

After losing a game on the road to the Cleveland Browns by a score of 21–14, the Steelers won three more straight and were 8–5 and fighting for a playoff spot with the loss of Roethlisberger and multiple injuries on the offense.

The Steelers would lose their final three games and finish the season with an 8–8 record in spite of multiple quarterback changes between Mason Rudolph and rookie undrafted free agent Devlin Hodges.

[47] Following an incident in November 2019 where Cleveland Browns defensive end Myles Garrett struck quarterback Mason Rudolph with a helmet in the closing minutes of the game, he initially refused all media questions related to the scuffle.

With the conclusion of the 2020 season, Tomlin was tied with Pete Carroll for 21st place on the NFL's all-time regular-season wins list with 145.

[55] The Steelers made the playoffs but saw their season end in the Wild Card Round to the Kansas City Chiefs in a 42–21 road loss.

[58] The 2022 season was Tomlin's 16th with the team, passing predecessor Bill Cowher for the second-longest tenure as head coach of the Steelers.

[59] December 11, 2022, marked the 32nd matchup between Tomlin and Baltimore Ravens head coach John Harbaugh, surpassing Curly Lambeau and Steve Owen for the second-most head-to-head matchups between head coaches in NFL history (the current record is held by Lambeau and George Halas with 49).

[69][70] Since the team's 2016 AFC championship appearance, the Steelers had yet to record a post-season victory, making Tomlin the coach with second longest playoff win drought in NFL history only behind Marvin Lewis.

[74][75][76] These phrases are typically concise, metaphorical, and aimed at reinforcing a specific mindset or message about the team and give insight into Tomlin's coaching philosophy.

Over time, these phrases became part of Steelers culture, with players adopting them as guiding principles and fans celebrating them as reflections of Tomlin's personality.

This quote became so widely used to represent the Steelers organization that the team had it engraved on the locker room walls at Heinz Field in 2013.

After a December 2020 win over the Indianapolis Colts, Tomlin stated "It's a fine line between drinking wine and squashing grapes.

[88] His approach has drawn criticism at times, notably when former Steelers quarterback and Hall of Fame member Terry Bradshaw referred to him as "more of a cheerleader guy" than coach during a 2016 interview.

[89] The 2018 season was plagued by locker room conflicts involving wide receiver Antonio Brown and running back Le’Veon Bell, highlighting discipline challenges under Tomlin's leadership.

[90] Meanwhile, Brown's issues, including disputes with quarterback Ben Roethlisberger and skipping practices, culminated in his benching for the season finale and eventual off-season trade to the Oakland Raiders.

[91] Critics argued these incidents reflected a lack of accountability in Tomlin's player-friendly approach, despite his strengths in fostering camaraderie.