Abstract: A compact, blower driven, fireplace air heater is provided that is adapted to be inserted into a conventional fireplace to increase the heat output thereof, and including a generally coplanar arrangement of a cool and a warm air manifold connected by a plurality of parallel, cool air conduits oriented perpendicularly with respect thereto. A plurality of warm air conduits are preferably arranged parallel to and coplanar with the cool air conduits, with each having one end terminating in the warm air manifold and the other, discharge end passing through the cool air manifold. Cool room air propelled by the blower is first warmed as it passes from the cool air manifold to the warm air manifold through the cool air conduits, and is further warmed as it passes from the warm air manifold through the warm air conduits prior to being discharged into the room through the discharge ends thereof.