The balance between preventing water flooding and adequate humidification of the membrane will provide a significant contribution to proton exchange membrane (PEM) fuel cell performance. For this purpose, polydimethylsiloxane (PDMS), a hydrophobic polymer, was added to the catalyst layer of the fuel cell at different amounts including 5, 10, and 20 wt%. The performances of the fuel cells including PDMS were compared with the commercial catalyst. Morphological changes of the gas diffusion electrodes (GDEs) were confirmed by using scanning electron microscopy (SEM). Fourier transformation infrared spectroscopy (FTIR) was used to determine the functional groups and contact angle measurements were used to determine the hydrophobic characteristics. Cyclic voltammetry (CV), impedance, and oxygen reduction reaction (ORR) analysis were performed for electrochemical characterization and degradation behaviors. In situ PEM fuel cell tests were performed in order to define the best catalyst ink combination that include PDMS. The results of the cyclic voltammograms proved that the electrochemical surface area (ECSA) increased with the increasing amount of PDMS. The highest ECSA of 53.84 m(2) g(-1) was calculated for catalyst ink with 20-wt% PDMS. The lowest ECSA loss after aging was observed in the catalyst ink with 10-wt% PDMS. As a result, the catalyst layer having 10-wt% PDMS showed the best polymer electrolyte membrane fuel cells (PEMFC) performance.