But the brewery may simply be sold to another beer company rather than shutting down altogether.
Molson Coors says it has entered into an agreement giving Pabst Brewing the option to buy the facility.
Pabst has 120 days to decide whether to buy the brewery at a price of $150 million, according to a Securities and Exchange Commission filing. As part of the deal, the companies are also dropping prior lawsuits against each other.
The brewery, which opened in 1980, is slated to cease production by September of this year.
It employs about 470 people and last year produced 4.8 million barrels of beer for brands which include Miller Lite, Coors Light, Miller High Life, MGD, Steel Reserve, Miller 64. The brewery also produces several brands for Pabst.
The brands produced in Irwindale will be shifted to breweries in Colorado and Texas.
"While it was a very difficult decision, we have extra capacity in our system and Irwindale's production can be absorbed by other breweries in our network," said Brian Erhardt, the company's chief integrated supply chain officer.