Bielema played college football as a defensive lineman at the University of Iowa under coach Hayden Fry from 1989 to 1992, serving as team captain his senior season. Bielema graduated from Iowa with a bachelor's degree in marketing. He went on to play for the Milwaukee Mustangs, a team in the Arena Football League.
In his first season as head coach of the Wisconsin Badgers in 2006, Bielema's team ended the regular season 11–1 (7–1 in Big Ten Conference play). With a 14–0 victory over San Diego State on September 16, 2006, Bielema became the third Wisconsin head coach to win the first three games of his career. Later, with a 24–3 win over Purdue on October 21, Bielema tied the record for most wins by a first-year coach at UW with seven. The other two coaches to complete this feat were Philip King in 1896 and William Juneau in 1912. A 30–24 victory over the Fighting Illini on October 28, Bielema became the first coach in Wisconsin history to win eight games in his first season. He then extended the record with his ninth victory on November 4, defeating the Penn State Nittany Lions, 13–3. With a 24–21 victory over the Iowa Hawkeyes on November 11, Bielema became the first head coach in Big Ten history to win ten games in his first season. With the 35–3 defeat of the University at Buffalo on November 18, 2006, Bielema became the first coach in UW history to win 11 games in the regular season. After a 17–14 victory over the Arkansas Razorbacks in the Capital One Bowl on January 1, 2007, he became the third coach in NCAA history to win 12 games in his rookie season, finishing 12–1.
Bielema coached Wisconsin to victories in 17 of his first 18 games. That represents the third-best start to a head coaching career in Big Ten history. Michigan's Fielding H. Yost, who went 55–0–1 from 1901 to 1905, and Ohio State's Urban Meyer, who won 24 straight games to begin his Big Ten career had better starts.
On October 16, 2010, Bielema's Badgers defeated #1-ranked Ohio State, 31–18, in Madison. It was Wisconsin's first victory over a #1-ranked team since 1981 when the Badgers upset Michigan. The victory against the Buckeyes would be his only one as he was 1-5 against Ohio State.
Bielema was named a finalist for the 2010 Bear Bryant Award which is given to college football's Coach of the Year. The other finalists were Chris Ault of Nevada, Gene Chizik of Auburn, Mark Dantonio of Michigan State, Jim Harbaugh of Stanford, Chip Kelly of Oregon, Gary Patterson of TCU, Bobby Petrino of Arkansas, and Mike Sherman of Texas A&M. The award was given to Chizik.
On December 4, 2012, it was announced that Bielema was leaving Wisconsin to become the head coach of the Arkansas Razorbacks. He left partly to play in the Southeastern Conference and partly because he felt that his assistant coaches were not being paid enough. Bielema replaced John L. Smith, who had coached Arkansas to a 4-8 record during the 2012 season after Bobby Petrino had been fired eight months earlier.
Bielema's first season at Arkansas resulted in an overall record of 3-9, including 0-8 in the Southeastern Conference. Bielema inherited a roster depleted of talent and lacking in development under lame-duck Coach Smith. Bielema's starting quarterback also suffered a throwing shoulder injury, which limited his ability the entire season. It was the Razorbacks' worst SEC record since entering the conference in 1992 and their first winless in-conference season since 1942, when they were a member of the Southwest Conference.
Bielema's second season saw significant improvement, as Arkansas finished 7-6. Bielema won his first two SEC games in dominating fashion in November, beating #17 LSU by a score of 17-0 and #8 Ole Miss by a score of 30-0 to achieve bowl eligibility. Though Arkansas lost its remaining conference game against Missouri, the Razorbacks were still the first unranked team in college football history to shut out two consecutive ranked opponents. Bielema led Arkansas to a Texas Bowl victory in the postseason, defeating Texas handily, 31-7.
In Bielema's third season, the team suffered the loss of returning 1,190 yard starting runningback before the season. Breaking in a new offensive coordinator and adjusting to losing three NFL drafted defensive players up front, the Razorbacks got off to a slow start, losing to Toledo and Texas Tech in the non-conference and started 2-4. Bielema then caught fire in the second half of the season, going 5-1 over the final six games, losing the one game on a missed field goal. Bielema ended the year by defeating one of his former mentors, Bill Snyder, in the AutoZone Liberty Bowl, as Arkansas dispatched Kansas State, 45-23, to finish the season with a record of 8-5.
Bielema's fourth season was a topsy-turvy campaign that ended with two embarrassing defeats at the hands of Missouri in the regular season finale and Virginia Tech in the 2016 Belk Bowl. The former saw his team blow a 17-point halftime lead and the latter was a 24-point blown halftime lead, which was the largest for Arkansas since at least 1952. Beating Missouri would have resulted in Bret Bielema improving his regular season record every year at Arkansas. The losses lead to the replacement of Defensive Coordinator Robb Smith with former Iowa State head coach Paul Rhoads, and other staff changes pointing to a change to a 3-4 defensive scheme.
Bielema is the highest paid state employee in Arkansas with a salary reported at $4,100,000. He is represented by sports agent Neil Cornrich.
*Ohio State was the Big Ten Leaders Division champion, but third place Wisconsin represented the division in the Big Ten Championship Game due to the fact that Ohio State and second place Penn State were both ineligible from post-season play by the NCAA.
‡Bielema left for Arkansas before the bowl game and the ranking reflects the team's ranking at the time of Bielema's departure.
Assistant coaches under Bret Bielema who became NCAA or NFL head coaches:Chris Ash: Rutgers (2016–present)
Paul Chryst: Wisconsin (2015–present)
Dave Doeren: Northern Illinois (2011–2012), NC State (2013–present)
Charlie Partridge: Florida Atlantic (2014–2016)
Bielema announced on April 1, 2011 that he was engaged to his girlfriend, Jen Hielsberg. They were married March 11, 2012 in Madison.
Arkansas sports radio personality Bo Mattingly debuted a series featuring Bielema entitled 'Being Bret Bielema' on February 25, 2016.
In December 2016, Jen Bielema announced via her Twitter account that she was pregnant. Bret later stated that they would be expecting the baby to arrive around July 2017, possibly during the 2017 SEC Media Days.