Regehr was signed as a free agent on July 6, 2004 as an undrafted player by the Calgary Flames, the team where his brother Robyn was playing. During the 2004–05 NHL lockout Richie Regehr played for the Lowell Lock Monsters, who were the American Hockey League affiliate of the Flames. In the 2005–06 season, he was sent to the Flames' new farm team, Omaha Ak-Sar-Ben Knights. After injuries to defencemen Rhett Warrener and Roman Hamrlík late in 2005, Regehr was called up to the Flames.