Disclosed are interconnection structures, semiconductor packages including the same, and methods of fabricating the same. The interconnection structure comprises a first dielectric layer, a wiring pattern formed in the first dielectric layer, a portion of the wiring pattern exposed with respect to a top surface of the first dielectric layer, a second dielectric layer on the first dielectric layer, the second dielectric layer including an opening that exposes the exposed portion of the wiring pattern, a pad formed in the opening of the second dielectric layer, the pad including a base part that covers the exposed portion of the wiring pattern at a bottom of the opening and a sidewall part that extends upwardly along an inner lateral surface of the opening from the base part, a first seed layer interposed between the second dielectric layer and a first lateral surface of the sidewall part, the first seed layer being in contact with the first lateral surface and the second dielectric layer, and a second seed layer that conformally covers a second lateral surface of the sidewall part and a top surface of the base part, the second lateral surface being opposite to the first lateral surface the second dielectric layer.