[1] He played college football for the Georgia Tech Yellow Jackets, winning the Fred Biletnikoff Award as a junior, and was selected by the Lions second overall in the 2007 NFL draft.

While still regarded as being in his prime, Johnson retired after the 2015 season, citing a loss of passion for the game due to health concerns and the Lions' lack of overall success during his tenure.

Johnson's parents stressed education in his childhood, forbidding him from playing sports if he didn't receive As and Bs in school.

15 player in the nation by TheInsiders.com, and named to the Super Southern 100 by the Atlanta Journal-Constitution, the Rivals 100 by Rivals.com, TheInsiders.com Hot 100, the SuperPrep All-America 275, and the Prep Star Top 100 Dream Team.

[2] In a mid-February workout with speed and conditioning coach Mark Pearsall, Johnson clocked a 4.33-second 40-yard dash, recorded an 11-foot standing broad jump, and had a vertical leap of 43 inches.

[74] On August 3, 2007, Johnson signed a six-year deal with the Detroit Lions after holding out for eight days, and passed his physical in time to be on the field for the start of that morning's practice.

[75][77] Although he did not start the game, Johnson had an impressive NFL debut on Sunday, September 9, 2007, catching four passes for 70 yards and his first career touchdown in Detroit's 36–21 win over the Oakland Raiders.

[82] Fellow teammate and wide receiver Roy Williams nicknamed Johnson "Megatron", due to his large hands being similar to that of the towering Decepticon.

[97] With Williams gone and starting quarterback Jon Kitna lost to injury for the season, the Texans defense had little to do to stop the Lions' offense but shut down Johnson, winning the game 28–21.

[99] During Week 10, formerly retired All-Pro quarterback Daunte Culpepper was signed to a one-year contract with the Lions in hopes to spur the offense and earned the starting job for the next two games.

[112] In the season opener against the Chicago Bears, Johnson caught a pass with 31 seconds left in regulation in the end zone for what looked like a game-winning touchdown.

[119] Following the 2010 season, Johnson was the recipient of the Lions/Detroit Sports Broadcasters Association/Pro Football Writers Association (Detroit Chapter) Media-Friendly Good Guy Award.

[134] Johnson beat out 42 other players and eliminated quarterback Cam Newton to win the Madden NFL 13 cover athlete on April 25, 2012, on SportsNation.

[149] After a slow start to the 2013 season in Week 1 against the Minnesota Vikings, Johnson had six receptions for 116 yards and two touchdowns in a 25–21 loss to the Arizona Cardinals.

[157] The second one gave him the Lions all-time record for touchdown catches with 63, breaking the old mark previously held by Herman Moore.

[164] Johnson started the 2014 season off strong with seven receptions for 164 yards and two receiving touchdowns in a 35–14 victory over the New York Giants on Monday Night Football.

[175] Johnson and Golden Tate became the Lions' first duo to reach 1,000 yards apiece in the same season since Roy Williams and Mike Furrey in 2006.

[179][180][181][182] In Week 5, a 42–17 loss to the Arizona Cardinals, Johnson caught his 671st career pass, breaking Herman Moore's franchise record.

[186] In Week 12, against the Philadelphia Eagles, Johnson caught eight passes for 93 yards and three touchdowns to help lead the Lions to their third straight victory and lift their record to 4–7.

[148][192] His 11,619 receiving yards rank fourth in a player's first nine seasons, trailing only Julio Jones (12,125), Torry Holt (11,864) and Jerry Rice (11,776).

[197] Despite spending his entire nine-year career with the Lions, Johnson did not partake in any events or attend games being played by his former team,[198] until 2023.

[201] More recently, Johnson's stance has softened as he attended several Detroit Lions team practices during the 2023 season and the September 17, 2023, home game against the Seattle Seahawks.

[202][203] Johnson was seen supporting the Lions at Ford Field as they secured their first playoff win since 1992 where they beat the Los Angeles Rams 24–23.

[232] In February 2019, Johnson and his wife Brittney were granted preliminary approval to open a medical cannabis dispensary in Michigan.

[233][234] He has since proceeded with plans to launch several cannabis facilities across the state (along with his business partner Rob Sims) under the brand name Primitiv.

[237] Also in August 2019, Johnson announced a partnership with Harvard University to study the effects of cannabis on chronic traumatic encephalopathy (CTE) and its benefits in managing pain.

[236] As part of the partnership, Johnson and Sims announced a six-figure donation to the International Phytomedicines and Medical Cannabis Institute at Harvard.

[238] In his Hall of Fame induction speech, Johnson noted his work with Harvard and the potential for plant-based medicines to "provide an alternative to their destructive counterparts, opioids".

[240] The foundation's goals include dedication to education, training, and social development of at-risk youth and providing financial aide to various community organizations.

[241] The Foundation hosts an annual camp called Catching Dreams, which aims to help high school wide receivers.