Olivia Newton-John has urged Federal Environment Minister Sussan Ley to protect koala habitat earmarked for clearing at Brandy Hill Quarry.
"We have so few left and we need to do something about it," she said in a video.
"What we need to do is keep their habitat, and there are 50 hectares of koala habitat being threatened by land clearing in Port Stephens.
"I'm asking our Australian Environment Minister Sussan Ley MP to please refuse the permit to bulldoze this land and help protect our koalas."
The quintessential performer went on to say how special koalas were to her and noted that they had already been through enough.
"Because of the loss of habitat through drought and of course fires and climate change and land clearing, our koalas are facing extinction by 2050 - and we must do something to turn this around," she said.
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Her calls were echoed by Jimmy Barnes, Magda Szubanski and Shaynna Blaze.
"The poor koalas are copping it again, you'd think after last year's bushfires, bulldozing 52 hectares of their habitat wouldn't be on anyone's radar. Please don't take any more from them," Barnes wrote on Twitter.
"Sussan Ley please save our koalas from extinction by saying no to to the Brandy Hill Quarry expansion which will destroy invaluable koala habitat," Blaze wrote on Facebook.
Szubanski asked her supporters to urge Ms Ley to refuse the expansion, saying "our precious koalas have suffered enough".
The support has bolstered residents who are working tirelessly to save the habitat.
Their social media campaign, 1 Day to Save Port Stephens Koalas, has attracted attention from across the globe.
"It's based on that fact that this is critical koala habitat, and it's a really important story," founder Chantal Parslow Redman said.
"When I started this I knew I had to have the science behind me and I had to prove what I was saying was true and have independent and expert advice."
Ms Ley is expected to make a decision about the project by October 13. She was initially supposed to decide on September 4
The state government approved the quarry expansion, and even fast-tracked it, in July. It was then passed to Ms Ley and her department due to its impact on the environment.
Quarry owner Hanson wrote in its application for approval that the expansion was vital to the future of the quarry and that it was running out of rock to extract. It also wanted to move its concrete plant to the quarry site.
If Hanson secures the approval the site will be offset through credits purchased nearby.