The 66-year-old man had been living alone and had been ill for a long time, and was found dead in his flat on November 11 by a neighbour who had been helping him.
The neighbour told Austrian broadcaster ORF that she notified the police about his death as she was unaware of any friends or family.
She assumed afterwards that he had been given a proper funeral — but suffered a shock when, on January 27, she accompanied a notary to help look for his will and found the body was still in the same spot.
“This is an unfortunate combination of circumstances and a communication problem” between the team certifying the death of the Viennese and the funeral services, said Nikolaus Salzer, director of the city's sanitation centre.
Salzer said he had launched an internal investigation into what he called an unprecedented case.
Contacted by AFP, the municipal funeral directors said they were yet to set a date for the funeral.
“We are still trying to find out if there are any family members who would like to organise it”, spokesperson Florian Keusch said.
If no relatives can be found, the funeral will be organised by the city.