American coal company Peabody Energy is cutting 170 staff at its Queensland and NSW mines. The company has also scrapped plans to fill another 230 positions.
Peabody has blamed short-term global economic challenges for the cost-saving measures that come just weeks after cutting 450 contracting jobs in June.
"The reduction has been made to align the company's workforce size with other cost reduction activities, as part of a comprehensive cost management review to secure the long-term competitiveness of our operations," the company said in a statement.
"We understand this decision affects our employees, families and their local communities, and we are supporting impacted employees and our workforce through this change."
Peabody operates eight mines in Queensland - seven in the Bowen Basin and one in the state's south-west. It also has three mines in NSW - in the Hunter Valley, in the state's central north and near Wollongong.
Many coalminers in Australia have been cutting jobs as they look to reduce costs in response to falling coal prices and the recent strength of the dollar.