An insulated flue protective assembly for insertion into a wall opening through which the chimney flue passes. The assembly comprises a square metal base unit having a center opening defined by a ring forming base flange. An insulated thimble is placed within the center opening defined by the ring, and is of a length so as to project to either side of the base unit. An elongated metal cover having at one end an annular flange forming a collar positionable about the ring of the base and which is adapted to receive an insulated sleeve, one end of which has mating contact with one end of the insulated thimble, thus insulating the chimney flue.