A fan-out semiconductor package includes a wiring portion, semiconductor chips, a dummy chip, and an encapsulant. The wiring portion includes an insulating layer, conductive patterns formed on the insulating layer, and conductive vias penetrating through the insulating layer and connected to the conductive patterns. The semiconductor chips are disposed on one region of the wiring portion, and the dummy chip is disposed on another region thereof and has a thickness smaller than those of the semiconductor chips. The encapsulant encapsulates at least portions of the semiconductor chips and the dummy chip. An upper surface of the wiring portion is disposed below a center line of the fan-out semiconductor package, and the thickness t of the dummy chip is such that T/2≤t≤3T/2 in which T is a distance from the upper surface of the wiring portion to the center line of the fan-out semiconductor package.