Police were called to the apartment after neighbors complained of a foul smell.
When they arrived, they expected the smell to come from the woman's hoarding, but were surprised to find that the woman was dead and the dog was starving.
The woman, Amparo C.R., was 72 years old and is thought to have died from natural causes as she had Alzheimer's.
The dog, a german shepherd mix, was found barking nearby and had his owner's blood on his fur.
An autopsy will be performed on the woman's body this week to determine the exact cause of death.
Police say the dog was not aggressive when he was found and is now at an animal shelter.
In the past, dogs that ate their dead owner's body have been adopted and integrated back into family life.
Celebrity dog trainer Brad Patterson spent time working with dogs that ate their dead owners and said they are usually normal, human compatible dogs.
"You just can't assume just because they've had human flesh, that they're going to become these creatures of the night, like a werewolf," he said.
"The only part of their temperament that has changed is the depression that they've lost something significant in their lives."