An interposer includes a base layer having a first surface and a second surface, a redistribution structure on the first surface, an interposer protection layer on the second surface, a pad wiring layer on the interposer protection layer, an interposer through electrode passing through the base layer and the interposer protection layer and electrically connecting the redistribution structure to the pad wiring layer, an interposer connection terminal attached to the pad wiring layer, and a wiring protection layer including a first portion covering a portion of the interposer protection layer adjacent to the pad wiring layer, a second portion covering a portion of a top surface of the pad wiring layer, and a third portion covering a side surface of the pad wiring layer. The third portion is disposed between the first portion and the second portion. The first to third portions have thicknesses different from each other.