Abstract: A forced air fireplace heating system for a space to be heated circulates air from the space through a lower horizontal plenum which either surrounds or is placed beneath the fireplace grill, and a series of adjustable tubes extending upwardly and forwardly from the rear of the plenum over the fireplace grill and through a front support into the space. A blower may be connected to either side of the plenum to draw air from the space for the purpose of heating and recirculating air back into the space. The system is self-contained and self-supporting within the fireplace requiring no modification or positive attachment to the fireplace or firebox itself; and accordingly is specifically adaptable for use in combination with a front closure for example of the type having glass doors across the front of the fireplace wherein the plenum extends through a panel section beneath the glass doors and the circulating tubes exit through a panel section above the doors.