A rugged positional player, Regehr was a WHL First Team All-Star in 1998-99 and a member of Canada's World Junior team who made his NHL debut with the Flames during the 1999-00 season. A key figure on the Calgary Flames young blueline, Regehr's career was uncertain after he was involved a car accident in 1999. Fully recovered from his injuries, Regehr impressed Team Canada officials with his stalwart play during the 1999-00 season and was invited him to play for Canada at the 2000 World Championships.

Known more for his physical presence on the ice, Regehr set a career high for points in 2003-04 with 18 (4-14-18) while helping the upstart Flames reach the Stanley Cup Final, only to lose in a hard-fought seven game series to the Tampa Bay Lightning.

Upon having his NHL season come to an end, Regehr helped Team Canada capture the 2004 World Cup title and in the spring of 2005 represented his homeland for the second time at the World Championship. A year later, Regehr was selected to represent Canada in the 2006 Winter Olympics.

In Calgary, Regehr established himself as one of the premiere defensive defenceman in the game, with seven straight seasons with a positive plus/minus rating.

On June 25, 2011, Regehr's time in Calgary would come to an end. He was traded along with Ales Kotalik and a second round draft pick to the Buffalo Sabres in exchange for Chris Butler and Paul Byron.

In his first season in Buffalo, Regehr would provide the solid, steady play that had become his trademark. In 76 games for the club, he would score just one goal, but would act as a stabilizing pressence on the Sabres blueline.

During the lockout shortened 2012-13 season, the Sabres found themselves near the bottom of the NHL's Eastern Conference standings. As such, they started trading off some of their higher-priced veterans. Regehr was sent to the Los Angeles Kings in the days leading up to the NHL trade deadline in exchange for Mark Cundari and pair of draft picks.