Johnson played college football in Morris Brown College in Atlanta, Georgia and was drafted in the first round of the 1977 NFL Draft by the Packers. He was a one time Pro Bowler in 1978 in a season in which he unofficially made 20.5 sacks. He had an official career best of 14.5 quarterback sacks in 1983 along with 107 tackles which is a team record for most by a defensive lineman in a single season. He played in 192 games in his career, making 55.5 quarterback sacks officially (99 with his unofficial totals added).
Johnson was most notable for eating a hot dog on the sidelines during the fourth quarter of a 38–0 Packers' home preseason loss to the Denver Broncos on August 30, 1980. Even though he was merely hungry and not insubordinate, he was fined $1,000 and required by then-general manager/head coachBart Starr to apologize to his teammates. Dissatisfied that the discipline was too lenient, defensive line coach Fred von Appenresigned in disgust five days after the incident.