Johnson was one of eight players to transfer to Brisbane when Fitzroy's AFL operations were taken over by the Brisbane Bears to form the Brisbane Lions and became the last Fitzroy Lion to play in the AFL.
Johnson is renowned for his creative play and composure running out of defence. Nevertheless, his 2007 preseason saw him playing as regularly in the forward line and the midfield as a defender, signalling the club's intention to use him as an impact player.
In the 2005 International Rules series, Johnson was named co-captain along with Andrew McLeod. In the second game of the series, Johnson started a brawl by clothes line tackling (or "coat hanger") Philip Jordan and striking Mattie Forde. He was suspended for five matches after pleading guilty to striking, ruling him out until the second Test in 2008.
Following his AFL career, he remained involved in the game.
He became a runner for the Brisbane Lions, appearing in Round 11 against Fremantle Dockers.
Then he shifted into coaching. On Friday 14 September 2007, Johnson signed on with the club as a full-time development coach for the Brisbane Lions. His job is to continue to assist in the development of the club's young playing list in the new position and to show off field leadership. He was promoted to assistant coach to Michael Voss.
He coached Brisbane school and AFL powerhouse St Peters Lutheran College for two years, posting a 10–0 record over his two-year tenure as the head coach for the opens team. They captured the 2007 and 2008 AIC AFL Premiership after defeating Iona College in the Grand Final on both occasions, before the competition was abandoned due to an increase of in game fights. In 2008, the school defeated Cairns school Djarragun College at the Gabba, before the Lions-Saints game, in an exhibition match to promote the AFL's indigenous round.