"I think this is going to be a new beginning for me in life," Khadr said after the ruling. "I just want to start anew now."
Rob Nicholson, Canada's justice minister, said the government would study the ruling closely before deciding whether to appeal.
Khadr is the eldest son of Ahmed Said Khadr, an alleged al-Qaeda member who was killed in 2003 by the Pakistani army.
Khadr's younger brother, Omar, is currently detained in the US prison camp at Guantanamo Bay. The US accuses him of killing an American soldier in Afghanistan in 2002.
The younger Khadr is scheduled to go on trial at Guantanamo later this month.
The United States paid the Pakistani government half a million dollars for Abdullah Khadr's capture, according to court records.