Joanne Cummings said she had to drive for two hours back home with the corpse in her hearse, with the air-condition going full blast to keep it cool.
"I actually had to turn around and drive two hours home to Roebourne (in Western Australia) and keep him in my car overnight," she told the Australian Broadcasting Corporation.
"I had to have the air-con up full and look after him that way, check on him every half hour, and the following morning we hired a sea container with a chiller unit in it."
She said a staff member described a 250-kilogramme dead man last year as "too fat, he can't go in the fridge".
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"You can't say things like that, imagine if this was your mother," Cummings told Port Hedland newspaper the North West Telegraph.
Western Australia's Country Health Service said the hospital's equipment could only handle bodies weighing up to 150 kilogrammes and that it would look into installing machinery that could take bodies of up to 300 kilogrammes.
But Cummings dismissed his claim that the hospital could not take in larger bodies as a "load of crap".
"I could probably put a baby elephant in one of those fridges and it'd fit through the door, and they're refusing entry for a human being," she said.
"My issue is if that was your father, mother, partner... you wouldn't want them refused entry into the mortuary.