The Seminole County Sheriff's Office said in a news release that the dog named Maxx helped firefighters find the 4-year-old boy and 2-year-old girl Monday night in their home in the Orlando suburb, Longwood.
Moments earlier, neighbors who saw the fire spreading called 911, broke windows and helped evacuate the children's mother, Margo Feaser.
Firefighters then were able to rescue Feaser's husband, as well as the two children with Maxx's help.
Feaser is an auto theft investigator with the sheriff's office.
Family members were hospitalized and their conditions ranged from serious to critical.
The dog was treated for smoke inhalation.