At the 2006 Winter Olympics, Morrison won a silver medal as part of the Canadian men's speed skating pursuit team.
Individually, Morrison won a silver in the 1500 m and a bronze in the 1000 m at a World Cup event in Turin in 2005–06.
In 2007, Morrison won gold in the 1000 metre event in Calgary in the World Cup finals with a time of 1:07:24.
He set a Canadian record, bettering his idol, Jeremy Wotherspoon.
In that same weekend, Morrison also won a bronze in the 1500 metre event.

Morrison also participated in the 2007 World Single Distance Championships, and achieved good results, winning three medals, bronze in the 1500 m and silver in the 1000 m, losing both times to Shani Davis.
In the team pursuit event he, along with Arne Dankers and Justin Warsylewicz, set an early best time, which broke the old team pursuit world record (previously held by Morrison, Dankers and Steven Elm), but the Dutch team of Sven Kramer, Erben Wennemars and Carl Verheijen would go on to beat the time set by Canada by five-tenths of a second, relegating Canada to 2nd place.

In 2008 Morrison topped his result from the year before at the World Single Distance Championships in Nagano, Japan.
He took the bronze medal in the 1000 meters, but won the 1500 m and took home the gold medal.
A week later, at the ING Finale at the Olympic Oval in Calgary, he set a new world record in the 1500 meters in a time of 1:42.01, beating the old record held by both Shani Davis and Erben Wennemars.

He competed at the 2010 Winter Olympics in Vancouver where he went in as a strong medal favourite in all three of his competitive events.
Despite competing on home ice Morrison was unable to win an individual medal, his best finish was a ninth in the 1500 m. He did find the medal podium though when he won a gold medal in the team pursuit along with Lucas Makowsky and Mathieu Giroux.
After the Olympics, Morrison considered retirement with some time away from summer training.
Eventually he re-joined the World Cup circuit and eventually finished the season winning silver at the 2011 WSD Championships, with his team pursuit team.
Re-motivated for 2012, he finished the season by winning his second World Championship title, again in the 1500 m. Morrison's 2013 season was off to a great start with an initial win at the first World Cup in Heerenveen, Netherlands, and finished the fall World Cup circuit leading the 1000 m points total so far.
Morrison then injured himself while training in Fernie, British Columbia, breaking his tibia.
At the time he was the leader of the 2012–13 ISU Speed Skating World Cup.
At the 2006 Winter Olympics, Morrison won a silver medal as part of the Canadian men's speed skating pursuit team. Individually, Morrison won a silver in the 1500 m and a bronze in the 1000 m at a World Cup event in Turin in 2005–06. In 2007, Morrison won gold in the 1000 metre event in Calgary in the World Cup finals with a time of 1:07:24. He set a Canadian record, bettering his idol, Jeremy Wotherspoon. In that same weekend, Morrison also won a bronze in the 1500 metre event.
Morrison also participated in the 2007 World Single Distance Championships, and achieved good results, winning three medals, bronze in the 1500 m and silver in the 1000 m, losing both times to Shani Davis. In the team pursuit event he, along with Arne Dankers and Justin Warsylewicz, set an early best time, which broke the old team pursuit world record (previously held by Morrison, Dankers and Steven Elm), but the Dutch team of Sven Kramer, Erben Wennemars and Carl Verheijen would go on to beat the time set by Canada by five-tenths of a second, relegating Canada to 2nd place.
In 2008 Morrison topped his result from the year before at the World Single Distance Championships in Nagano, Japan. He took the bronze medal in the 1000 meters, but won the 1500 m and took home the gold medal. A week later, at the ING Finale at the Olympic Oval in Calgary, he set a new world record in the 1500 meters in a time of 1:42.01, beating the old record held by both Shani Davis and Erben Wennemars.
He competed at the 2010 Winter Olympics in Vancouver where he went in as a strong medal favourite in all three of his competitive events. Despite competing on home ice Morrison was unable to win an individual medal, his best finish was a ninth in the 1500 m. He did find the medal podium though when he won a gold medal in the team pursuit along with Lucas Makowsky and Mathieu Giroux. After the Olympics, Morrison considered retirement with some time away from summer training. Eventually he re-joined the World Cup circuit and eventually finished the season winning silver at the 2011 WSD Championships, with his team pursuit team. Re-motivated for 2012, he finished the season by winning his second World Championship title, again in the 1500 m. Morrison's 2013 season was off to a great start with an initial win at the first World Cup in Heerenveen, Netherlands, and finished the fall World Cup circuit leading the 1000 m points total so far. Morrison then injured himself while training in Fernie, British Columbia, breaking his tibia. At the time he was the leader of the 2012–13 ISU Speed Skating World Cup.
Denny Morrison