The approximately 5-month-old puppy, who has been named Bambi by the Delco SPCA staff because she resembles the fragility of a baby deer, is just 7 pounds.
Officials say a dog her age should be three times her current weight.
The mother dog, who the Delco SPCA staff has named Faline after a character in the movie Bambi is also malnourished, weighing just 26 pounds.
As a young adult dog, she should weigh at least 40 pounds.
The dogs were discovered Monday morning by the constable after an eviction notice was posted on the door of the home.
The Delco SPCA is investigating the situation to determine the owner responsible for the neglect and abandonment of the dogs, which appear to be merle Pit Bull Terrier blends.
SPCA officials say the dogs will be on a regimented feedings throughout the day and night as well as receive supplements and any other necessary veterinary care.
They say both dogs are responding well to the care but the puppy remains in critical condition.
The SPCA is asking donations for the care of Bambi and Faline. To support their care, visit http://delcospca.org/donations/.