Provided is a thermally conductive silicone composition that can be turned into a lightweight cured product superior in thermal conductivity, and is easily processable due to its low viscosity. The composition contains: (A) an organopolysiloxane having at least two alkenyl groups per each molecule; (B) an organohydrogenpolysiloxane having, per each molecule, at least two hydrogen atoms directly bonded to silicon atoms; (C) a thermally conductive filler containing magnesium oxide (20 to 40% by mass), aluminum oxide (40 to 60% by mass) and aluminum hydroxide (10 to 30% by mass); (D) a dimethylpolysiloxane with one end of the molecular chain thereof being blocked by a trialkoxy group; (E) a platinum group metal-based curing catalyst; and (F) an addition reaction control agent.