The 83-year-old died in 2009, police said, and had been kept for so long by her daugher, now 55, that her body had become mummified where it lay in the bed.
A local social worker had become suspicious after neighbours in the city district of Blumenau informed the building manager that they hadn't seen the pensioner for a long time.
After trying several times to make an appointment by phone and being met with excuses by the daughter, he visited the apartment in person.
When the daughter wouldn't open the door, he called the police. They and the fire service were able to get the door open and discovered the body inside in a double bed which the daughter had been sharing.
The daughter later admitted during questioning that her mother had died during March of 2009. She has been sent to a psychiatric institution.
An autopsy produced no evidence of foul play in the mother's death.