Khadr pleaded guilty in 2010 to war crimes, including throwing the grenade that killed U.S. Army medic Sgt. First Class Christopher Speer during a firefight in Afghanistan on July 27, 2002.
U.S. troops captured Khadr, who was then 15 years old and near death, at a suspected al Qaeda compound the day of the attack. He recently turned 26.
He also pleaded guilty to attempted murder, providing material support for terrorism, conspiracy and spying.
The plea agreement called for serving one year of confinement in the United States, and then transferring Khadr to Canada to serve the remainder of his sentence.
The Obama administration delayed the transfer and the Canadian government took additional time to work out a plan to hold Khadr, according to news reports.
“The United States coordinated with the government of Canada regarding appropriate security and humane treatment measures," the Defense Department said in a statement.
"In accordance with statutory reporting requirements, the administration informed Congress of its intent to transfer Khadr to Canada.”
There are still 166 detainees at Guantánamo Bay.