A heat dissipating assembly suited for an electronic device is provided. The electronic device has at least one heat source. The heat dissipating assembly includes a first tube, a second tube, and a fluid. The first tube has an inlet and an outlet, wherein a bore size of the inlet is smaller than a bore size of the outlet. Heat generated from the heat source is transferred to the first tube. Two opposite ends of the second tube are connected to the inlet and the outlet such that the first and the second tubes are formed into a closed loop. The fluid is filled in the closed loop. The fluid in the first tube transferred from the inlet toward the outlet absorbs the heat and is transferred to the second tube for heat dissipating. An electronic device is also provided.