The invention provides a semiconductor package assembly. The semiconductor package assembly includes a first semiconductor package including a first semiconductor die. A first molding compound surrounds the first semiconductor die. A first redistribution layer (RDL) structure is disposed on a bottom surface of the first molding compound. The first semiconductor die is coupled to the first RDL structure. A second redistribution layer (RDL) structure is disposed on a top surface of the first molding compound. A passive device is coupled to the second RDL structure.