A heat-dissipating semiconductor package and a fabrication method thereof are provided. A semiconductor chip is mounted and electrically connected to a substrate. A heat-dissipating structure includes a heat sink and at least one supporting portion, wherein the supporting portion is attached to the substrate at a position outside a predetermined package area for the semiconductor package, and the semiconductor chip is disposed under the heat sink. An encapsulant is formed on the substrate to encapsulate the semiconductor chip and the heat-dissipating structure, wherein a projection area of the encapsulant on the substrate is larger in size than the predetermined package area. A cutting process is performed along edges of the predetermined package area to remove parts of the encapsulant, the supporting portion and the substrate, which are located outside the predetermined package area, so as to form the semiconductor package integrated with the heat-dissipating structure.