The blaze reported at 12:15 a.m. Saturday in the Homewood section of the city damaged four buildings, including a church, causing damage estimated at about $280,000.
The Animal Rescue League said the dog, Sophie, was found Monday morning covered in soot and ashes in the basement of one of the homes that caught fire.
Rescuers said the floor above the dog was ready to fall in. The white boxer, a female about five years old, is being treated with oxygen for smoke inhalation.
League officer Erica Daniels said she will be reunited with her family when she's well enough to go home.