“A group of around 230 ‘cetaceans’ have washed ashore near Macquarie Harbour,” the Tasmanian state Department of Natural Resources and Environment said.
“It looks like about half of the animals are alive,” he added.
Aerial footage showed a desolate scene where dozens of sea mammals were scattered along a wide beach.
Authorities said marine conservation experts and a team with cetacean rescue equipment were on their way to the area.
Almost two years ago to the day, the area was the scene of another mass stranding, with nearly 500 pilot dolphins stranded, of which around 100 survived.
The reasons for these large strandings are not fully known.
Scientists have suggested they could be caused by groups of cetaceans straying after feeding too close to shore.
Pilot whales being very social animals, they can follow members of their group who get lost and find themselves in danger.