ALCOA last week announced it will close Australia's largest aluminium mill and recycling plant in Yennora.
At least 180 jobs will be lost when the plant shuts its doors at the end of the year.
Alcoa announced it would close three facilities throughout Australia, costing a total of 980 jobs.
An Alcoa spokesman said: "The decision to close these facilities has not been taken lightly and we understand how difficult it is for our employees and their families.
"We are committed to supporting our employees through this transition.
"All benefits and entitlements will be paid out and the company will provide financial planning, confidential counselling services and out-placement services."
Blaxland MP Jason Clare said that many of the employees have worked at the Yennora plant for up to 30 years.
"This is shocking, terrible news for Alcoa workers and their families," Mr Clare said.
"My focus is on the 180 workers and their families from the Yennora plant. We have to do everything possible to help them get back on their feet.
"The Abbott Government needs to provide adjustment packages and transition assistance for these workers."
State Deputy Premier Andrew Stoner said, despite the recent setbacks to the industry, innovative manufacturing had a bright future in Australia and particularly in western Sydney, which is the home of roughly 8500 manufacturing companies.
"It is always disappointing to see workers lose their jobs," he said.
"And unfortunately the decision by Alcoa reflects the many challenges facing the manufacturing industry, including relatively high input costs such as electricity and the impact of the carbon tax, as well as wages and the impacts of the high Australian dollar."
Mr Stoner said the NSW Liberals and Nationals government was committed to supporting the manufacturing industry and cited two pilot programs worth $2.6 million designed to help manufacturing companies find new business and become globally competitive.
It's little comfort for Vince Purcell, who has worked at Alcoa's plant in Yennora for 28 years. He said the closure came as a shock.
"We were notified two weeks ago that this plant was under review. Up until then, we were told our grandkids would have jobs here," he said.
The Yennora plant has operated in south-west Sydney for more than 40 years and produces approximately 55,000 tons of scrap aluminium yearly.
It also produced 125,000 tonnes of rolled aluminium for use in food and beverage cans.
It was also the only aluminium mill and recycling plant in NSW.