Johnson was born and raised in Wangaratta, Victoria. He played junior football with the Wangaratta Football Club, before moving onto the Murray Bushrangers in the TAC Cup. He was selected by Geelong with pick 24 in the 2001 AFL Draft. His first few years were plagued with inconsistency, injury and off field problems. A medium-sized forward, Johnson is renowned for his freakish ability on the field, where he has consistently wowed fans with his penchant for extraordinary goals. As a child, Steve was a natural left footer.
Johnson was suspended by his club for the first five matches of the 2007 season after he was arrested for public drunkenness in Wangaratta on 24 December 2006 - a charge which was later dropped. He returned in Round 6 against Richmond where he went on to contribute 21 possessions and two goals in a match Geelong won by 157 points. He went on to post career-best numbers across the board, capped off by All-Australian selection on the half-forward flank in September.
His 2007 season was capped off when Johnson lead the Cats to victory in the Grand Final, collecting a premiership medallion, and winning the Norm Smith Medal for best on ground in the Grand Final. Johnson was hailed as a feel good story for the year, with a good example of a player reforming after disciplinary action.
Early in 2008 however, Johnson lost his drivers' license and was sentenced to 50 hours working with the TAC after he was clocked in over 70 km/h over the speed limit in a 50 zone. Teammate Shannon Byrnes was in the car at the time.
He had yet another stellar season in 2008, kicking 49 home-and-away season goals and earning a spot on the forward flank in the All-Australian team of 2008. He gathered 34 disposals in the Cats' Grand Final loss to Hawthorn.
In 2011, 'Stevie Wonder', struggled to consistently produce the captivating form that had won him All Australian selection in previous years. He was still a force though, gaining recognition by being honored in the initial All-Australian squad of 40. His season nearly came to an abrupt end, when during the third quarter of the Preliminary Final between Geelong and West Coast, he appeared to sustain a serious injury to his left knee. Racing against the clock in order to gain fitness for the Grand Final against the Magpies, it was heavily speculated that Johnson would be unable to gain full fitness in time. For almost the entire week, whilst his team-mates trained in the spotlight, Stevey J spent time up in Melbourne in a Hyperbaric Chamber. Fortunately for himself and Geelong fans, Johnson was able to gain fitness needed and played a vital part in the cats win over the Pies. He went on to kick 4 goals amongst 14 possessions, thus claiming his third premiership medallion.