The four, who are in their early 20s, became caught on an ice shelf about 150 metres from shore behind the Supreme Court of Canada, Ottawa Fire spokesman Marc Messier said. The canoe had taken on water and there were concerns over the fast currents, he said.
"They were not intoxicated," Messier told CBC News. "They had canoed there in the past and they were just out canoeing."
The current caught them and they ended up against the ice shelf," he said. "They weren't able to get away. They hung on to the ice shelf."
Messier added that none had life jackets.
Firefighters had to use inflatable water rescue rafts that can be used on ice and water to secure the individuals and keep them safe until they could get additional resources to bring them ashore, Messier said.
He said the canoeists were brought back to shore two at a time.
"They're fine. They weren't wet," Messier told CBC News. "They were a little cold but they were OK. And once we got them to shore they were assessed by paramedics and released."