Johnson attended Wake Forest from 2010 to 2014. As a true freshman, he played in 11 games with five starts. In 2011, he redshirted after being ruled academically ineligible. He returned in 2012 as a starter and remained as the starter throughout his senior season. Johnson finished his career with 189 tackles and seven interceptions.
The Houston Texans selected Johnson in the first round of the 2015 NFL draft. He was the second cornerback selected in 2014, behind Michigan State'sTrae Waynes. On May 8, 2015, the Houston Texans signed Johnson to a fully guaranteed four-year, $10.04 million contract with a signing bonus of $5.50 million. Throughout training camp, he competed against A. J. Bouye for the job as the third cornerback on the depth chart. Head coach Bill O'Brien named Johnson the third cornerback on the Texans' depth chart, behind veterans Johnathan Joseph and Kareem Jackson. He made his professional debut in the Texans' season opener against the Kansas City Chiefs and recorded two solo tackles in the 27–20 loss. On October 4, 2015, he made a season-high five solo tackles in his first career start in a 48-21 loss to the Atlanta Falcons. The next game, Johnson had his second consecutive start and made five combined tackles in a 27–20 loss to the Indianapolis Colts. In Week 8, Johnson had one of the best games of his rookie year when he recorded a season-high six combined tackles and a pass deflection, and intercepted Titans'quarterbackZach Mettenberger for his first career interception. He returned the interception for 22 yards and helped the Texans defeat the Titans, 20-6. Johnson finished his rookie season with a total of 54 combined tackles, nine pass deflections, and an interception while playing in all 16 games and starting ten.
2016
The following season, Johnson returned as the Texans' third cornerback and made two solo tackles in their season-opening victory over the Chicago Bears. The following week, he made four solo tackles in a 19–12 victory over the Kansas City Chiefs. On October 2, 2016, he made his first start of the season and racked up two solo tackles during the Texans' 27–20 win over the Tennessee Titans. On October 16, 2016, Johnson recorded a career-high nine solo tackles, one assisted tackle, and a pass deflection in the Texans' 26–23 defeat of the Indianapolis Colts. He broke his foot during the game and was placed on injured-reserve on October 22, 2016. In his absence, A. J. Bouye emerged as a sufficient replacement. Johnson finished his second season with 25 combined tackles and three pass deflections in six games and three starts.
2017
Johnson entered training camp competing with Kareem Jackson for the job as the starting cornerback after A. J. Bouye signed with the Jacksonville Jaguars. He started the Houston Texans' season-opener against the Jacksonville Jaguars and recorded five combined tackles during their 29-7 loss. The following week, he recorded four combined tackles in a 13–9 victory over the Cincinnati Bengals. He left during the third quarter after suffering a sprain to his MCL and was estimated to miss the next four-six weeks. On October 29, 2017, he played in his first game since returning from his MCL injury and recorded five combined tackles and deflected a pass during a 41-38 loss to the Seattle Seahawks. Kareem Jackson earned Johnson's starting cornerback job during his absence and remained the starter after his return. He played in 12 games overall in 2017, starting four, recording 45 tackles and two pass deflections.
2018
On April 30, 2018, the Texans picked up the fifth-year option on Johnson's contract. In Week 1 against the New England Patriots, Johnson suffered a concussion and was placed on injured reserve on September 12, 2018.
2019
On March 5, 2019, Johnson was released by the Texans.
On March 11, 2019, the Buffalo Bills signed Johnson to a one year deal. He played in 16 games with one start, recording 36 tackles, five passes defensed, and one sack.
Cleveland Browns
On April 4, 2020, Johnson signed a one-year contract with the Cleveland Browns.
Personal life
Johnson is childhood friends with former NFL wide receiver Michael Campanaro. They attended high school and college together.