Disclosed herein are a package substrate and a fabricating method thereof. The package substrate includes a substrate including at least one conductive pad, an insulation layer formed on the substrate and including an opening through which the conductive pad is exposed, a blister prevention layer formed along a top surface of the conductive pad exposed through the opening and a sidewall of the insulation layer, a metal post made of at least one alloy material and formed on the blister prevention layer, and a heat-diffusion prevention film formed on the metal post.