Stellantis has decided to shutter the Windsor Assembly Plant for two weeks starting on Monday.
The company notified Unifor Local 444 after U.S. President Donald Trump made his "Liberation Day" announcement.
As expected, Trump confirmed a 25 per cent tariff on foreign-made automobiles and parts.
"While we had heard rumours of potential downtime, the company said there are multiple factors at play, with the primary driver behind the final decision being made after this afternoon's announcement from U.S. President Donald Trump," said the union.
The threat of tariffs has created uncertainty across the auto industry.
Meanwhile, there's word Stellantis is temporarily laying off 900 workers at five American facilities. The factories are stamping and powertrain plants. There have been additional layoffs at plants in Mexico.
"Unifor warned that the U.S. tariffs would hurt auto workers almost immediately, and in this case, the layoffs were announced before the auto tariff even came into effect," said Unifor National President Lana Payne. "Trump is about to learn how interconnected the North American production system is the hard way, with auto workers paying the price for that lesson."
Unifor represents more than 4,500 Stellantis workers at the Windsor Assembly Plant, with additional members at auto parts plants across the region.
Unifor has called on Ottawa to increase supports for workers impacted by the trade war.