Following high school, he chose to play college football for the South Carolina Gamecocks after receiving scholarship offers from two other teams.

He helped lead Murphy High School to a 10–2 record and a 6A Regional runner-up finish his senior year, earning a spot on the Alabama Sports Writers Association All-State team.

[4] In 2006, he earned a second-place finish in the long jump event at the AHSAA State T&F Meet, recording a career-best leap of 6.85 meters (22 ft, 4.75 in).

[6] After his high school career, Munnerlyn was recruited by South Carolina, West Virginia, and Kansas State.

[9] In the same game, South Carolina wide receiver Kenny McKinley fielded a punt and flipped it to Munnerlyn who gained eight yards.

[17] Munnerlyn called being drafted by the Panthers, "exciting, because I played college ball at South Carolina, and that's only like an hour away.

[18] He eventually won the punt return job as well as the primary nickel cornerback spot beating out C. J. Wilson and Sherrod Martin (who was selected 157 picks before Munnerlyn) by the end of September.

[20] In a Week 16 game at the New York Giants, he forced a fumble by quarterback Eli Manning on the last play of the first half.

In his first start of the season in Week 12 against the Cleveland Browns, Munnerlyn stepped in front of a pass from Jake Delhomme intended for Mohamed Massaquoi to pick it off and return it 37 yards for the touchdown.

Playing in 16 games with five starts, Munnerlyn recorded 47 tackles and one forced fumble, tied for second on the team with three interceptions (including one returned for a touchdown) and ranked first with 10 passes defensed, contributing to a Panthers defense that ranked seventh in the NFL in average yards per play.

Through 10 days of the Panthers' spring practice, Munnerlyn tutored Murphy's defensive backs as part of veteran coach Ronn Lee's staff.

In Week 5 at New Orleans Saints on October 9, he registered his first career sack, dropping quarterback Drew Brees for a six-yard loss on a blitz.

In a Week 8 game against the Minnesota Vikings, he got his second sack of the season when he tackled Christian Ponder for a one-yard loss after he scrambled to the right to escape from pressure.

Later in the game, he also stripped and recovered a fumble by Vikings wide receiver Percy Harvin a yard shy of the endzone.

He also batted down six passes and was credited with two quarterback pressures, contributing to a unit that ranked 10th in the NFL in total defense.

In Week 5 against the Seattle Seahawks, he intercepted a pass by quarterback Russell Wilson and returned it 33 yards for a touchdown.

In Week 11, he picked off a pass by Buccaneers quarterback Josh Freeman and returned it 74 yards for a touchdown, his second of the year.

[22] Prior to the start of training camp, Munnerlyn told ESPN, "I want to help my team get to the playoffs," he said.

In Week 6 at Minnesota, he ripped the ball away from Vikings running back Adrian Peterson to force a fumble.

On December 15, he set the franchise record with his fifth career interception return for a touchdown after he picked off Jets' quarterback Geno Smith and returned it 41 yards for the score, surpassing the previous mark of four by Mike Minter from 1997 to 2006; in that game, he also established a single-game career high with two sacks as he brought down Smith for losses of seven and eight yards.

At the end of the season, he finished tied for fourth on the team with 7 passes defended and ninth in total tackles with 61.

Munnerlyn ended his first year with the Vikings with 61 combined tackles, one fumble recovery, 2 interceptions and 5 pass deflections.

He helped the Vikings defensive unit rank fifth in the NFL in defensive points allowed at 18.9 points per game, playing a key role in the Vikings winning the NFC North title over long-time reigning champs Green Bay Packers for the first time since 2009.

In the final game of the regular season against the Green Bay Packers for the NFC North title, the Vikings had a 13–3 lead with just over four minutes remaining in the third quarter.

On a 3rd-and-12 play, Aaron Rodgers dropped back to his own 45-yard line to make a pass, but Vikings defensive end Everson Griffen got a hand on Rodgers' arm, causing him to fumble; Munnerlyn scooped up the ball at the 55-yard line and with blocking support from safety Andrew Sendejo and linebacker Anthony Barr, ran it all the way back for a touchdown (his first on a fumble recovery).

[26] Munnerlyn recorded 55 tackles, a sack, one fumble recovery for a touchdown, two interceptions, and four pass deflections in his second season in Minnesota.

"[14] Munnerlyn majored in criminal justice while at South Carolina, where he was teammates and roommates with former Viking linebacker Jasper Brinkley.

On January 24, 2025, Munnerlyn was named head coach of the Julius L. Chambers High School football team in Charlotte, North Carolina.