The Kabul-based trainers are to help prepare Afghan national police and army soldiers to assume security duties, Canada's defence minister said.
The 2,800 Canadian troops currently in Afghanistan face a parliamentary deadline to return home in 2011.
The non-combat trainers are to stay until 2014.
“Our goal is not merely to do things for Afghanistan and the people of Afghanistan,” Conservative Foreign Affairs Minister Lawrence Cannon told reporters on Tuesday.
“It is also to help them do things for themselves once more after decades of civil war and chaos in government.”
Ministers said the 950 troops would not be involved in combat, and that training – in firearms, physical fitness, infantry, armour and logistics – would take place in classrooms and bases in Kabul, rather than in the field.
“There will be no mentoring” on the battlefield, Mr McKay said.
The new details of the extension came a day after the leader of the Liberal opposition party demanded details of the plan and the New Democratic Party leader criticised the extension of the mission as “the wrong thing to do”.
In announcing the extension last week, Conservative Prime Minister Stephen Harper said he did not need parliament's approval for the move, leading the leftist New Democrats and separatist Bloc Quebecois to accuse him of breaking a promise to bring 2,800 troops home this summer.
The announcement comes ahead of a Nato summit in Lisbon later this week.