His father was in Winnipeg working at the local Canadian Imperial Bank of Commerce (CIBC) branch when he transferred to Fort Frances, Ontario, in 1985 for an assistant manager position.

[3] Keith grew up as a Boston Bruins fan, singling-out defenceman Ray Bourque and forward Cam Neely as his favourite players, as well as Wayne Gretzky.

"[3] While Keith began to be recruited for AAA Bantam in Thunder Bay, Ontario, his father obtained a managerial position at a CIBC branch in Summerland, British Columbia.

He completed his freshman year with 3 goals and 15 points in 41 games, ranked fourth among team defencemen behind John-Michael Liles, Brad Fast and Andrew Hutchinson.

He made an immediate impact on the club, scoring nine goals and 12 assists for 21 points, while averaging over 23 minutes of ice time in 81 games during his 2005–06 NHL rookie season.

He added 6 points in 17 playoff games as the Blackhawks advanced to the Western Conference Finals, where they were eliminated by Central Division rivals, the defending Stanley Cup champion Detroit Red Wings.

[11] Entering the 2010 playoffs as the second seed in the Western Conference, the Blackhawks eliminated the Nashville Predators, Vancouver Canucks and San Jose Sharks in the first three rounds.

He returned minutes after the incident to help the Blackhawks complete a four-game sweep of the Sharks and advance to the Stanley Cup Finals for the first time since 1992.

Nominated for the James Norris Memorial Trophy for his regular season performance, he outvoted Mike Green and Drew Doughty of the Los Angeles Kings to earn the award as the NHL's best defenceman in the off-season.

Facing the Presidents' Trophy-winning Vancouver Canucks in the first round of the playoffs, the defending Stanley Cup champion Blackhawks were eliminated in seven games.

Head of the Department of Player Safety Brendan Shanahan observed that the hit was "dangerous, reckless, and caused injury" in his video release.

[12] On June 4, 2013, Keith received a one-game suspension for a slash to the face of Los Angeles Kings' forward Jeff Carter during Game 3 of the Western Conference Finals.

The league, in announcing the suspension, referred to the slash as "a one handed upward swing" which struck Carter directly in the face causing a laceration which required 20 stitches to close.

[14] Keith recorded four goals and seven assists in the 2014 playoffs, but lost to Los Angeles Kings in the Western Conference Finals, the eventual champions.

On March 29, 2016, Keith was checked to the ice by Minnesota Wild forward Charlie Coyle and retaliated with his stick—Coyle required medical attention having blood dripping from his nose.

[19][20][21] In late-June 2021, it was reported that Keith had requested a trade from the Blackhawks to Western Canada or the Pacific Northwest of the United States to be closer to his family (who live in Penticton, British Columbia) as he finished out his career.

[22] On July 12, Keith's sixteen season run with the Blackhawks came to an end when he, along with Tim Söderlund, were traded to the Edmonton Oilers in exchange for Caleb Jones and a conditional third-round pick in 2022.

[27] Despite the controversy, Keith was generally regarded as having performed solidly in his debut season in Edmonton, recording one goal and 20 assists for 21 points in 64 games played, largely on the second pair.

Keith also played on Canada's gold medal-winning team at the Ice hockey at the 2014 Winter Olympics – Men's tournament in Sochi.

[39][40] On February 25, 2014, Keith, along with Blackhawks teammate Brent Seabrook, made a cameo appearance on the NBC drama Chicago Fire.