The fire started about 10:45 Sunday night in the unit at the Northgates apartment complex on East 19th Street.
Firefighters had it out in about 15 minutes, but it was too late for the tenant who died at the scene.
Investigators believe the fire started in the living room. They aren't saying what might have caused it, but they are saying they don't believe the fire was started intentionally.
Apartment managers say the victim used an oxygen tank to breathe, so any type of smoke inhalation could be fatal.
Jimmy Talley of the Panama City Fire Department said, "We will go back out and take a second look and see if the autopsy confirms where we feel like the fire started."
Investigators have not released the victim's name. They're still trying to notify his family.