Jeff Taylor, president of the Air Canada unit of the Canadian Union of Public Employees, said nearly 88 percent of the flight attendants who voted rejected the deal negotiated last month. Nearly 79 percent of Air Canada's approximately 6,800 flight attendants voted.
"The results send a strong message to the company," Taylor said in a news release. "We have heard our members loud and clear.
"After a decade of concessions, the membership has clearly said it wants a fair deal, especially since the company is in a much better financial position."
Taylor said the next steps would be to arrange for a strike vote next month and to resume contract negotiations with Air Canada management.
Air Canada said little in a statement other than to note the contract had been rejected, the CBC said.
The airline's pilots also turned down a proposed contract this year, and Air Canada is negotiating with its mechanics and baggage handlers, as well.
Pensions are key issue for Air Canada's union employees, the CBC said.
Air Canada, wrestling with rising fuel costs, lost $46 million in the quarter ended June 30.