He played college football for the Oregon Ducks and was selected in the second round of the 2009 NFL draft by the Patriots, where he spent 11 non-consecutive seasons.

[5] After redshirting in 2004, Chung took over at the "rover" position in 2005, ranking second on the team with 91 tackles (5 solo), as he caused a fumble and deflected five passes.

He averaged 22.3 yards on nine kickoff returns while leading the Ducks with a career-high 117 tackles (71 solos), adding 7.5 stops for loss.

[7] Chung garnered Third Team All-American accolades in addition to making the All-Pac 10 first-team for the second consecutive year in 2008.

[11] On January 24, 2009, Chung participated in the 2009 Senior Bowl as part of Cincinnati Bengals' head coach Marvin Lewis' North team that lost 18–35 to the South.

[16] The second round pick used to select Chung was previously traded from the Kansas City Chiefs to the Patriots in exchange for Matt Cassel and Mike Vrabel.

[19][20] Head coach Bill Belichick named Chung the backup strong safety to begin the regular season, behind Brandon Meriweather.

He made his first NFL tackle with teammate Darius Butler on cornerback Leodis McKelvin during a 21-yard kick return in the fourth quarter.

[25] Chung finished his rookie year with 37 combined tackles (25 solo), two sacks, a pass deflection, and an interception in 16 games and one start.

[32] On October 4, 2010, Chung made five combined tackles and returned an interception by Chad Henne for a 51-yard touchdown to mark the first score of his career.

He also blocked a punt and a field goal as the Patriots routed the Miami Dolphins 41–14 on Monday Night Football in Week 4.

[36] Chung finished his second NFL season with 96 combined tackles (72 solo), nine pass deflections, three interceptions, and a touchdown in 14 games and 13 starts.

On January 16, 2011, Chung made his first NFL start in a playoff game and recorded four solo tackles during a 28–21 loss to the New York Jets in the AFC Divisional round.

[35] With 1:14 left in the second quarter, Chung made the decision to call an audible on a punt and opted to receive a direct snap from the long snapper on a trick play instead and attempt to gain four-yards for the first down.

[38] The mistake proved costly as the New York Jets capitalized on their field position and scored a touchdown in four plays and 41 seconds to enter half time leading the Patriots 14–3.

[43] On October 30, 2011, he collected a season-high 13 combined tackles (ten solo) and broke up a pass in the Patriots' 25–17 loss at the Pittsburgh Steelers in Week 8.

[44] On February 5, 2012, Chung started in Super Bowl XLVI and recorded six combined tackles and a pass deflection in the Patriots' 21–17 loss to the New York Giants.

He was reunited with Eagles' head coach Chip Kelly, who served as Oregon's offensive coordinator during Chung's last two years.

The competition included Chung, Kenny Phillips, Colt Anderson, Nate Allen, Kurt Coleman, and David Sims.

[56] In Week 6, Chung made two combined tackles before exiting the Eagles' 31–20 win at the Tampa Bay Buccaneers in the third quarter after aggravating his shoulder injury.

[57] On December 29, 2013, Chung collected a season-high ten combined tackles (five solo) during a 24–22 win at the Dallas Cowboys in Week 17.

On January 4, 2014, Chung made four solo tackles in the Eagles' 26–24 loss to the New Orleans Saints in the NFC Wildcard Game.

[61] Head coach Bill Belichick named Chung the starter to begin the season, alongside free safety Devin McCourty.

[72] Two weeks later, Chung collected a season-high 11 combined tackles (seven solo) and two pass deflections in the Patriots' 27–16 win at the Pittsburgh Steelers.

[73] On February 5, 2017, Chung recorded five combined tackles and two passes defended as the Patriots defeated the Atlanta Falcons by a score of 34–28 in overtime to win Super Bowl LI.

[77] Head coach Bill Belichick retained Chung and McCourty as the starting safety duo to open the 2017 regular season.

[78] In Week 10, Chung collected four solo tackles, broke up a pass, and returned an interception by Brock Osweiler for 30 yards in the Patriots' 41–16 win at the Denver Broncos.

[83] Chung was injured early in the second half of Super Bowl LIII against the Los Angeles Rams, sustaining a "right hand or wrist injury."

[95] On October 26, 2021, Chung was charged with assault after allegedly pushing a woman to the ground, slapping her face, and breaking her phone outside her home in Milton, Massachusetts.

[96] Chung and former teammate Nate Ebner are minority owners of Major League Rugby's team New England Free Jacks.