The Sacramento Bee newspaper reported that a social worker heard the toddler crying while making a visit to check on the family Thursday morning. The worker called police after no one answered the door.
Inside, authorities found the body of 36-year-old Lisa Gonzales. It was not immediately known how she died, but a Child Protective Services spokeswoman says the woman suffered from a chronic illness.
A Sacramento police spokesman says foul play was not suspected.
The boy, identified only as Noah, is in protective custody while social workers determine whether he can be placed with a family member.