OTTAWA — Unifor, Canada’s largest private sector union, reached a tentative agreement with the Ford Motor Company of Canada early Tuesday, concluding contract talks with the three Detroit-based automakers.

As with the Canadian branches of General Motors and Fiat Chrysler Automobiles, the union focused on preserving jobs as much as traditional contract issues like wages.

Jerry Dias, the union’s national president, said that the company would invest about 700 million Canadian dollars, or $522 million, to introduce a new engine at one of three engine factories Ford has in Windsor, Ontario. He said that the two older of those Windsor factories, which had been widely expected to close, would probably remain open.

“Are we better off today than we were yesterday in Windsor?” Mr. Dias said. “The answer is yes.”

He added that with the new investment, the company’s employment in the city would probably increase.