A couch-surfing koala has taken winter shelter in the lounge room of a coastal NSW house, sitting in the living room in front of a heater.

Port Stephens resident Vicki Haines and her partner Michelle stumbled across the furry intruder on Tuesday night when they arrived home.

"Michelle was the first inside and she started yelling out 'there's a koala on the couch!'" Ms Haines told AAP.

"She was hiding behind a mountain bike wheel and our dog was going crazy.

"But when things calmed down it was pretty cute, it was just sitting right in front of the heater where I usually sit with my dog."

It is believed the young male koala got inside through the doggie door.

Hunter Koala Preservation Society care and rescue coordinator Simone Aurino was called to relocate the mischievous marsupial.

She said the area was a known native animal corridor between two patches of bushland.

"There's an increasing trend of koalas being caught in garages, roofs and in people's backyards," Ms Aurino said.

Despite their cuddly appearance, koalas can use their long claws to inflict severe scratches.

"They've got quite long talons and any cornered animal will defend themselves, so they did the right thing by keeping their distance," Ms Aurino said.

The koala, dubbed Tuff Bugger, was microchipped and peacefully released back into the wild.

Ms Haines said she'll make sure windows, doors and doggy doors are closed when she goes on holiday this weekend.

"Hopefully we don't come back and find a whole family of koalas inside."