In a statement, Harper referred to the hijacking of four aircraft by al-Qaida terrorists as "senseless and cowardly" and said the declaration of a commemoration was to "honor the nearly three thousand innocent people from 90 countries who lost their lives in the attacks and pay respect to their family and friends who still suffer."
Harper recalled how the 10,000 people of Gander, Newfoundland, opened their homes to thousands of air passengers who were diverted from their destinations by the attacks.
"I hope that this National Day of Service, observed hereafter on Sept. 11, will inspire Canadians to once more show the same kind of compassion to strangers in need, by engaging on that day in charitable activities, fundraisers and community service for worthy causes across the country," the prime minister said.
Separately, Gov. Gen. David Johnston issued a statement of support and condolence.
"I would like to pay tribute to the innocent victims whose lives were cut short as a result of this senseless attack," he wrote. "My thoughts go out to their families and loved ones, who relive the anguish every year on this tragic date."