Johnson was selected by the Toronto Blue Jays in the 1993 Major League Baseball draft, then made his MLB debut on April 6, 1997 with the Baltimore Orioles going on to play for the Orioles (1997) and Montreal Expos (1997–2001).

He was a member of the Team Canada baseball team at the 2004 Summer Olympics, where they finished in fourth place in the tournament.

Johnson played in the Texas Rangers, Los Angeles Dodgers, and San Francisco Giants organizations from 2001 through 2003, before signing with the Expos again in 2004.

In 2006, Johnson played with Somerset of the independent Atlantic League. In 2007, he played for the Edmonton Cracker-Cats of the Northern League. In 2008, he played for the CPBL's La New Bears and won the winningest pitcher and the MVP at the regular season.

On March 7, 2009 he pitched again for Canada in the World Baseball Classic against the USA. For the 2009 season, he signed to play for the SK Wyverns in South Korea after an interval of four years, but was dismissed in April having appeared in just two games. He then signed with the Edmonton Capitals of the Golden Baseball League, for whom he finished the season. He split the 2010 season between the Capitals and Yuma Scorpions.

He is presently a coaching instructor in Edmonton for the St. Francis Xavier high-school baseball Academy.

• Career statistics and player information from Baseball Reference, or Fangraphs, or Baseball Reference (Minors)