Johnson attended Highland High School in Gilbert, Arizona from 2007 to 2009, before transferring to Findlay Prep in Henderson, Nevada for his junior year.

[1] In November 2010, he signed a National Letter of Intent to play college basketball at the University of Arizona.

[1][3] In his junior season, he earned first-team All-Pac-12 and Pac-12 All-Defensive team honors, as well as being named the Pac-12 Player of the Year.

[8] During his rookie season, he received multiple assignments to the Rio Grande Valley Vipers of the NBA Development League.

[9] On July 20, 2015, the Rockets traded Johnson, Joey Dorsey, Kostas Papanikolaou, Pablo Prigioni, a 2016 first-round draft pick, and cash considerations to the Denver Nuggets in exchange for Ty Lawson and a 2017 second-round draft pick.

[13] On September 8, 2016, Johnson signed with the Orlando Magic,[14] but was waived on October 22 after appearing in four preseason games.

[15] On October 29, 2016, Johnson signed with Bayern Munich of the German Basketball Bundesliga till the end of the season.

[21] On January 16, 2019, Johnson was acquired by the Wisconsin Herd with returning right of Olivier Hanlan and a second-round pick in the 2019 NBA G League Draft for Travis Trice.