A semiconductor package includes a base package substrate, a first semiconductor chip, and a second semiconductor chip. The base package substrate includes a redistribution region where a redistribution layer is provided, a plurality of vertical conductive vias connected to the redistribution layer, and a recess region recessed from an upper surface of the redistribution region. The base package substrate further includes an interposer in the recess region, the interposer comprising a substrate, a plurality of upper pads disposed at an upper surface of the substrate, and plurality of through electrodes respectively connected to the plurality of upper pads to pass through the substrate. The first semiconductor chip and second semiconductor chip, each include a plurality of conductive interconnection terminals respectively connected to the plurality of upper pads and the vertical conductive vias exposed at the upper surface of the redistribution region. The first semiconductor chip and the second semiconductor chip are mounted on the extension region and the interposer and disposed horizontally apart from each other. As seen from a plan view, the interposer is disposed to overlap a portion of each of the first semiconductor chip and the second semiconductor chip.