A woman lived with her dad's corpse for around 15 years until she died herself, police said.
Police only discovered both bodies after neighbours reported a foul smell coming from the home.
The woman, aged between 55 and 65, is thought to have died of natural causes last month.
But her deceased 80-year-old father was found wearing pyjamas in bed in a mummified state.
Neighbours told the police that they hadn't seen the man in at least 15 years.
According to local media, his documents expired back in 2005.
Residents said that the woman was always alone and rarely spoke to anyone in the area.
Police were shocked by the man's remains in the bedroom on April 16.
The man moved in with his daughter in the village of Linda-a-Velha, Oeiras, Portugal, when he was widowed in 2001.
Firefighters had to enter the rubbish-filled property through a window after being unable to force the door open.
There were no signs of a crime inside the home and both victims are believed to have died of natural causes.
The authorities will carry out analysis on the bodies to establish their exact causes of death and when they passed away.
The police found the home full of rubbish, but neighbours said they hadn't noticed a foul smell until the last couple of weeks.
The investigation is ongoing.
Last month, police discovered a man who was believed to have been living with a decomposing corpse in Texas, US.
It is understood the man, in his 60s, was living with the corpse for months before taking his own life.
A man in his 60s is believed to have been living with a decomposing corpse for several months before taking his own life, police have said.
Cops were called to a home in northwest Harris County after a neighbour sensed a foul odour and thick flies began flying out of the property.
Moments before they entered the property, officers heard a gunshot and went inside to discover a man on the bedroom floor with a self-inflicted gunshot wound.
Another man's body, who was around the same age, was found in a separate room, which had been severely decomposing for months, authorities said.
The relationship between the two men is unclear, but they appeared to have been living together in the house.
Detectives are investigating the case of death of the decomposed body.
