"Jason is leaving [Thursday] and should be in the lineup Friday," Canadian general manager Ken Holland told the Canadian Press on Wednesday.
Canada plays its first game of the tournament Friday against Denmark.
"Jason had a breakthrough year in his career, getting 21 goals and over 50 points," said Holland, who is also Detroit's GM. "He'll be a good addition to Canada because he's a good skater and he played in Finland during the lockout and has experience on the big ice."
The 25-year-old Williams, a native of London, Ont., had one goal and one assist in the playoffs.
The Canadian team now has 13 players after Scott Hartnell, Dan Hamhuis and Stephane Robidas were named to the team on Tuesday.
Holland said three or four other NHL players could be added before the end of Wednesday.
Already signed up for duty are forwards Patrice Bergeron, Kyle Calder and Mike Comrie along with goalie Marc Denis and defenceman Nick Schultz, who are all gold medallists at previous world championships.
Defenceman Brad Stuart was part of the team that won in 2001.
Vancouver goalie Alex Auld, Pittsburgh star Sidney Crosby and Brad Boyes of Boston will make their tournament debuts.
All three also played for Canada in the world junior championship.
