A structure of a package on package and a method for fabricating the same are provided. The structure of the package on package includes a first package, a second package and a plurality of pins. The first package includes a first substrate and a first chip disposed thereon. The second package includes a second substrate and a second chip disposed thereon. The second package is disposed under the first package. The second package includes a plurality of holes. The pins are disposed on the first package and inserted to the holes so as to electrically connect the first package and the second package.