Adams played college football for the Delaware Fightin' Blue Hens, and was signed by the San Francisco 49ers as an undrafted free agent in 2004.

Adams also played for the Cleveland Browns, Denver Broncos, Indianapolis Colts, Carolina Panthers, and Houston Texans, and made two Pro Bowls during his 16-year career.

[2] Throughout training camp, he competed for a roster spot as a backup safety, cornerback, and special teams player against fellow rookie Keith Lewis.

On September 4, 2004, the San Francisco 49ers waived Adams as part of their final roster cuts, but signed him to their practice squad two days later after he cleared waivers.

He appeared in the San Francisco 49ers' season-opener against the St. Louis Rams and recorded four solo tackles, two pass deflections, an interception, and made his first career sack on quarterback Marc Bulger in their 28–25 victory.

[10] On September 27, 2005, head coach Mike Nolan announced he'd be moving Adams from nickelback to starting free safety after Rumph sustained a foot injury.

[7] Throughout training camp, Adams competed to retain his role as the starting free safety against Keith Lewis and Tony Parrish.

[18][19] Head coach Romeo Crennel named Adams the backup free safety, behind Brodney Pool, to begin the regular season.

[21] Adams was limited to a backup role and did not receive any starts in 2007, but managed to finish the season with 29 combined tackles (27 solo), a pass deflection, and a sack in 16 games.

[7] He entered training camp in 2008 and competed for a roster spot as a backup safety against Gary Baxter, Nick Sorensen, and Steve Cargile.

Head coach Romeo Crennel retained Adams as the backup free safety behind Brodney Pool to start the 2008 regular season.

[24] In Week 3, Adams made his second start at strong safety in place of Jones and recorded four combined tackles, a pass deflection, and an interception during a 28–10 loss at the Baltimore Ravens.

[28][29] Throughout training camp, Adams competed for the starting strong safety job against Abram Elam after Sean Jones departed for the Philadelphia Eagles during free agency.

[30] Head coach Eric Mangini named Adams the primary backup safety to start the regular season, behind starters Abram Elam and Brodney Pool.

[33] Head coach Eric Mangini named Adams the backup free safety to start the season, behind Abram Elam.

[34] He started in the Cleveland Browns' at the Tampa Bay Buccaneers and collected seven combined tackles, made a season-high three pass deflections, and an interception in their 17–14 loss.

[35] On December 5, 2010, Adams recorded three combined tackles, a pass deflection, and an interception in the Browns' 13–10 victory at the Miami Dolphins in Week 13.

He intercepted a pass by quarterback Chad Henne that was deflected by Browns defensive lineman David Bowens and returned it 25-yards to the two-yard line.

[43] On November 11, 2012, Adams recorded four combined tackles and sacked quarterback Cam Newton for a safety in the Broncos' 36–14 victory at the Carolina Panthers in Week 10.

[43] Throughout training camp, Adams competed to retain his starting strong safety role against David Bruton, Duke Ihenacho, and Quentin Jammer.

[45] Head coach John Fox named Adams the backup strong safety to start the season, behind Duke Ihenacho.

[48] He started in place of Rahim Moore who underwent surgery to repair a lateral compartment syndrome and missed the remainder of the regular season.

[48] Before the start of Super Bowl XLVIII, Adams vowed to walk about 12 miles (19 km) from MetLife Stadium back to his childhood home if the Broncos were victorious.

[51] Adams became an unrestricted free agent after the 2013 season and received interest from several teams, including the San Francisco 49ers, New York Jets, Cleveland Browns, and New England Patriots.

[54] Throughout training camp, he competed for a job as the starting strong safety against Delano Howell, David Sims, Colt Anderson, and Sergio Brown.

[58] On November 16, 2014, Adams tied his season-high of 11 combined tackles (eight solo), deflected two passes, and intercepted quarterback Tom Brady twice during the Colts' 42–20 loss to the New England Patriots in Week 11.

On January 7, 2015, Adams started in the AFC Wildcard Game and collected nine combined tackles (seven solo) and a pass deflection during the Colts' 26–10 win against the Cincinnati Bengals.

[66] In Week 9, Adams made one tackle, a pass deflection, and an interception, but exited the Colts' 27–25 win against the Denver Broncos in the third quarter after injuring his ankle.

Head coach Ron Rivera officially named him the starter entering the regular season, opposite strong safety Kurt Coleman.

[75] On October 1, 2017, Adams collected a season-high seven solo tackles and two pass deflections in the Panthers' 33–30 victory at the New England Patriots in Week 4.