John Phillips does not say where Khadr has been sent or when the move happened.
But a source tells The Canadian Press he was moved to Bowden Institution, a medium-security prison near the town of Innisfail.
The transfer had been expected for several weeks.
In a statement, Phillips says he hopes the move is a first step in getting Khadr the appropriate treatment he needs.
Khadr pleaded guilty in 2010 to five war crimes, including murder, for killing an American soldier in Afghanistan when he was 15.
The 27-year-old is being held at the federal maximum-security prison in Edmonton where he is serving the remainder of an eight-year sentence.
Khadr was transferred to Canada from a U.S. military base in Guantanamo Bay in September 2012.
"As Omar's counsel, Dennis Edney and I are pleased to see Canada finally acknowledge that Omar is not a dangerous individual," Phillips said in the statement Tuesday.
"We trust that this is the first step by Canada in providing Omar with treatment that is appropriate for someone who is a former child soldier."
Arlette Zinck, a professor at King's University College in Edmonton, said talks are under way in the expectation that Khadr can take high school courses while he is at Bowden.
Zinck is one of a group of professors who have been helping Khadr improve his education.
"There will be a way to work with Bowden for sure, we are in conversation," she said.
Last October an Alberta judge turned down his request to be moved to a lower security provincial jail where he would be eligible for rehabilitation programs.
At the time Public Safety Minister Steven Blaney welcomed the court ruling, saying the government of Canada would continue to vigorously defend against any attempt to lessen his punishment.
The Correctional Service of Canada would not confirm Khadr's transfer, citing federal privacy rules.
Bowden Institution is a medium-security prison with a minimum-security annex.
A government website says Bowden Institution encourages inmates to become law-abiding citizens by offering education, employment, and rehabilitation programs.