Defence, security and aerospace company BAE Systems will slash 100 positions by year's end, primarily in South Australia.
Chief executive David Allott says the job cuts are due to reduced government defence spending and increased competition in Australia.
"Our focus is strategic and aimed at improving business efficiency so that we can continue to be highly competitive and 'fit for the future' in what is an increasingly tough market," Mr Allott said.
"These are difficult decisions and we are mindful of the impact these reductions have on our team. Natural staff turnover and redeployment will be used where possible and we will do everything we can to support those employees who are affected."
The company's Land and Integrated Systems Business Unit and corporate functions will also be restructured and more closely aligned.
In addition BAE System's Mawson Lakes operations will move to the company headquarters at Edinburgh Parks before the end of 2013.
The changes are expected to save the company $15 million annually.
BAE Systems employs about 1,100 people in South Australia and 5,000 nationally.
SA Premier Jay Weatherill says the loss of jobs is always disappointing.
He believes the company is seeking voluntary redundancies and the job cuts arise out of the consolidation of their two offices in South Australia.
"While that is regrettable, the company advises that it is to try to give them some efficiencies to allow them to win more contracts," he told reporters on Monday.
The company had recently missed out on some contracts and the government obviously wanted them to be more successful too, Mr Weatherill added.
He also said BAE Systems was a strong company which remained committed to South Australia.