Johnson was born in Andalusia, Alabama. He attended Andalusia High School, where he played basketball under coach Richard Robertson, as well as football. He recorded 78 tackles, 32 assists, one fumble recovery, one blocked punt and 11 interceptions during his senior season. As a junior, he made 80 tackles and blocked one field goal attempt.
Johnson received ASWA first team All-State honors three consecutive times and was named to the Orlando Sentinel′s All-Southern Team and the Press Register′s Super Southeast 120 (No. 12). He also earned All-American honors by Parade, was a finalist for the High School Butkus Award, and was selected U.S. Army All-American Bowl, where he led the West squad with four solo tackles, including two tackles for loss.
In the 2013 NFL Draft, Johnson was selected by the Kansas City Chiefs in the fourth round with the 99th overall draft pick. Johnson signed a 4 year, $2 million deal with the Chiefs. On August 30, 2014 he was released during final preseason roster cut downs. The next day he was signed to the Chiefs practice squad.