A native of Edmonton, Alberta, Derek Morris starred for the AMHL's Red Deer Chiefs before joining the WHL's Regina Pats in the fall of 1995. Chosen 13th overall by the Calgary Flames in the 1996 NHL Entry Draft, Morris went on to play two seasons in Regina, registering 75 points during the 1996-97 season and being named to the WHL East First All-Star Team.
The young blueliner made a smooth transition to the NHL in 1997-98. He recorded 29 points and played aggressive defence, earning himself a place on the NHL's All-Rookie Team. Morris continued to be one of the club's leaders at both ends of the ice but was unable to get the Flames into the post season. A contract holdout caused Morris to miss a large portion of the 2000-01 season, however, upon his return he averaged 25 minutes of ice time during the last 51 games of the schedule.
After five seasons in Calgary, Morris was dealt to the Colorado Avalanche prior to the 2002-03 season, in a trade that saw Chris Drury head to Calgary. Upon his arrival in Colorado, Morris went on to establish a career high in points with 48 (11-37-48). In 2003-04, Morris struggled offensively compared to his previous year and was subsequently traded to the Phoenix Coyotes at the trading deadline along with prospect Keith Ballard for Chris Gratton and Ossi Vaananen.
On the international stage, Morris is a three-time member of Canada's World Championship team (1999, 2001 and 2004), capturing gold in 2004.
At the 2009 NHL trade deadline Morris was sent to the New York Rangers in exchange for a package of players that included Dmitri Kalinin, Petr Prucha and Nigel Dawes.
In the summer of 2009, Morris found himself on the move again. This time he was an unrestricted free agent and decided to leave the bright lights of Broadway for the old world charm of Boston and join the Bruins.
On March 3, 2010, the NHL trade deadline, the Bruins sent Morris back to a familiar place when they shipped the defender to the Phoenix Coyotes in exchange for a fourth round draft pick.