A fan-out semiconductor package includes a core member having a through-hole. A semiconductor chip is in the through-hole and has an active surface with connection pads and an inactive surface opposing the active surface. An encapsulant encapsulates at least portions of the core member and the semiconductor chip and fills at least a portion of the through-hole. A connection member is on the core member and the active surface of the semiconductor chip and includes a redistribution layer electrically connected to the connection pads. The core member includes a groove portion penetrating from a wall of the through-hole up to an outer side surface of the core member in a lower portion of the core member on which the connection member is disposed.