In this work, a new density-modulated platinum thin film (Pt-TF) design was fabricated by high pressure sputtering deposition (HIPS) and was investigated as potential electrocatalysts for the ORR in PEMFCs using cyclic voltammetry and rotating disk electrode techniques in aqueous perchloric acid electrolyte. Scanning electron microscopy and X-ray diffraction methods were used to study morphological and crystallographic properties of the density-modulated Pt-TF electrocatalysts. The Pt-TF catalyst was produced by changing working gas pressure from low to high values during film growth, which results in denser film bottoms and more porous tops. Low-density film top provides effective transportation of oxygen, which could enhance catalyst utilization and result in reduced Pt-loading and enhanced activity. Porous yet interconnected network of Pt atoms in the low-density Pt-TF surface can also eliminate the agglomeration and dissolution problems. In addition, high-density film bottom provides a strong adhesion to the substrate leading to enhanced physical and electrochemical stability of the Pt-TF. Stronger bonds along with self-protection against the acidic environment due to the dense-packing of Pt atoms at the interface with the substrate can hinder leaching of Pt and avoid the detachment of large regions of Pt-TF from the substrate as a whole. In addition, high-density layer can reduce contact resistance and enhance the electronic conductivity. This presentation will focus on electrochemically active surface area, area specific activity, and mass activity of density-modulated Pt-TFs during accelerated stability tests and compare them to conventional high-density Pt-TF and Pt/C electrocatalysts.