Abstract: An heated pet sweater including a sweaterlike garment worn by a pet wherein the garment has one or more pockets disposed thereon. The pockets are generally of construction permitting substantially free passage of thermal energy to the body of the animal wearer and being thermally isolated otherwise and furthermore the pockets have thermal energy generation devices employing chemical reaction, direct energy storage, or latent heat of fusion energy storage for providing heat to the animal at substantially constant temperatures for extended periods. An alternate embodiment provides for cooling of an animal using latent heat energy extraction means disposed in pockets of an animal worn garment.