Brooks attended C. D. Hylton High School in Woodbridge, Virginia, where he helped lead two VHSL state championships during his freshman and sophomore year (1998 and 1999).

Becoming recognized, Brooks' team was nationally ranked, going 40–0 before losing to Potomac High School of Woodbridge, Virginia, during his junior season in 2000.

He earned a starting position on the Virginia Cavaliers football team as a freshman and finished the year with a career-high and team-leading 117 tackles.

He had a career-high 12 tackles against Pittsburgh in the Continental Tire Bowl, including a key stop early in the contest to complete a goal-line stand.

Brooks earned Atlantic Coast Conference defensive lineman of the week honors for his performance against the Maryland Terrapins.

Brooks finished the year with 27 tackles (10 solo), a sack, four pass deflections, and five quarterback pressures in only six games.

Brooks entered the NFL supplemental draft following his junior season at Virginia and was selected by the Bengals in the third round on July 13, 2006.

[5] In the next game against the Carolina Panthers, Brooks recorded five tackles, a pass deflection, and his first NFL sack as the Bengals won by a score of 17–14.

[8] During the season opening 27–20 victory over the Baltimore Ravens on Monday Night Football, Brooks was the starting middle linebacker and recorded six tackles and a strip-sack.

[9] However, in the first series of the next game against the Cleveland Browns, Brooks tore his groin muscle, prematurely ending his season.

[16] In the next game against the Arizona Cardinals on Monday Night Football, he had four tackles and single-game career-highs of three sacks and two forced fumbles during the 24–9 victory.

[19] During a Week 2 25–22 loss to the New Orleans Saints on Monday Night Football, Brooks recorded two tackles and his first sack of the season.

[21] Brooks earned his first start as a 49er in Week 13 against the Green Bay Packers and finished the 34–16 road loss with four tackles and two sacks.

[22] In the regular season finale against the Cardinals, Brooks recorded four tackles, a sack, a pass deflection, and his first NFL interception during the 38–7 victory.

[31] Brooks finished the 2011 season with a career-high 50 tackles, seven sacks, three pass deflections, and a forced fumble in 16 games and starts.

[39] During a Week 8 24–3 road victory over the Cardinals on Monday Night Football, Brooks recorded two tackles and a sack.

[41] Two weeks later against the Saints, he recorded five tackles, 1.5 sacks, a pass deflection, and his first NFL interception which was returned for a touchdown in the 31–21 road victory.

[44] Brooks finished the 2012 season with 48 tackles, 6.5 sacks, six pass deflections, two forced fumbles, and an interception returned for a touchdown in 16 games and starts.

[46] During the NFC Championship Game against the Falcons, Brooks had two pass deflections in the 28–24 comeback road victory as the 49ers earned a trip to Super Bowl XLVII.

[47] In the Super Bowl against the Baltimore Ravens, he recorded five tackles and a sack, but the 49ers fell behind early and could not come back, losing by a score of 34–31.

[50] During a Week 7 31–17 road victory over the Tennessee Titans, Brooks recorded a tackle, a pass deflection, and a sack.

[52] In the next game against the Saints, Brooks had two tackles, a strip-sack, a fumble recovery, a pass deflection, and an interception during the 23–20 road loss.

[54] During a Week 12 27–6 road victory over the Redskins on Monday Night Football, Brooks recorded seven tackles, two sacks, and a pass deflection.

[75] During the season-opening 28–0 shutout victory over the Los Angeles Rams, Brooks recorded three tackles and his first sack of the season.