Born in Laval, Quebec, Jose Theodore played with the Richelieu Riverains in the Quebec Midget AAA Hockey Leauge. In 1992-93, he joined the QMJHL's St-Jean Lynx and played there for parts of three years. He was selected 44th overall by the Montreal Canadiens at the 1994 NHL Entry Draft then spent the better part of the 1994-95 season with the Hull Olympiques. During the 1994-95 season, he led the league 32 wins and helped his club reach the Memorial Cup tournament.
A member of Canada's Gold Medal World Junior team in 1996 and the tournament's Top Goaltender, Theodore split his first four professional seasons with Montreal and Fredericton of the AHL. He made 30 appearances in 1999-00 and recorded five shutouts with an impressive 2.10 goals against average and was a member of Canada's World Championship team where he was named to the Second All-Star Team.
During the 2000-01 season, Theodore became a workhorse for the Canadiens after a season-ending injury to Jeff Hackett and became the team's number one netminder the following year. The 2001-02 season was a dream season for the Laval, QC native leading the Habs to their first playoff appearance in four years and capturing numerous awards including the George Vezina Trophy as Top Goaltender and the Hart Memorial Trophy as Most Valuable Player.
Coming off a career year in 2001-02, Theodore and the Canadiens struggled the in 2002-03, missing the post season, yet rebounbing in 2003-04 with a career high 33 wins, and was subsequently named to Canada's entry in the 2004 World Cup of Hockey. Following a lock-out year in 2004-05, Theodore struggled with the Habs in 2005-06 and just prior to the NHL trading deadline was dealt to the Colorado Avalanche in exchange for netminder David Aebischer.
In his first full season in Colorado, Theodore struggled and posted a 13-15-1 record with a 3.26 GAA. He rebounded in 2007-08 and toward the end of the season was dominant in leading the Avalanche back into the playoff picture. Despite their turnaround, the Avs were quickly defeated by the eventual Stanley Cup champion Detroit Red Wings that year and Theodore became an unrestricted free agent in the summer.
On July 1, 2008, Theodore signed a two year nine million dollar contract with the Washington Capitals.
During the 2009-10 season, Theodore pledged money to the Saves for Kids program, which benefits the Neonatal Intensive Care Unit at the Children's National Medical Center, for each save, win and shutout he recorded. When the season was over he was able to present the program with a cheque worth $35,000. For his efforts he was awarded the Masterton Trophy for his perseverance and dedication to hockey.
On October 1, 2010, he signed a one-year deal with the Minnesota Wild. Theodore would spend just one season in Minnesota, posting 15 wins and a solid 2.71 goals-against-average.
In the summer of 2011, again an unrestricted free agent, Theodore signed on with the Florida Panthers.