Package structures and methods of forming the same are disclosed. One of the package structures includes a first die, a second die, a dummy substrate and an encapsulant. A bottom surface of the second die is adhered to a top surface of the dummy substrate through a glue layer, and a total area of the bottom surface of the second die is different from a total area of the top surface of the dummy substrate. A total thickness of the first die is substantially equal to a total thickness of the second die, the dummy substrate and the glue layer. The encapsulant is disposed aside the first die, the second die and the dummy substrate.