An integrated fan-out package includes a die, an encapsulant, a seed layer, a conductive pillar, a redistribution structure, and a buffer layer. The encapsulant encapsulates the die. The seed layer and the conductive pillar are sequentially stacked over the die and the encapsulant. The redistribution structure is over the die and the encapsulant. The redistribution structure includes a conductive pattern and a dielectric layer. The conductive pattern is directly in contact with the seed layer and the dielectric layer covers the conductive pattern and surrounds the seed layer and the conductive pillar. The buffer layer is disposed over the redistribution structure. The seed layer is separate from the dielectric layer by the buffer layer, and a Young's modulus of the buffer layer is higher than a Young's modulus of the dielectric layer of the redistribution structure.