Electroless deposition is a simple and scalable method to deposit a thin layer of Pt in the membrane that has been demonstrated in a number of studies [1]–[6]. Recent advancements in the deposition method has enabled deposition of an ultra-thin Pt layer in Nafion (< 200 nm) [5], but no thorough study with respect to the impact of deposition parameters on the physical structures and fuel cell performance has been reported in the literature. For fuel cell applications, it is essential to design an optimum platinized membrane structure which maximizes Pt utilization while minimizing the Pt loading. In this study, the ultra-thin electroless deposited layers with various loadings were studied and characterized physically and electrochemically. Grain size and ECSA characterization from XRD and CV analysis indicate that inter-particle electrical connectivity was improved as the Pt loading increased, until the loading reached a value of about 52 μg_Pt/cm² (Figure 1). Fuel cell polarizations and constant current operation under different humidity levels were examined with the additional electroless deposited Pt layers at loadings below 45 μg_Pt/cm² than for the standard MEAs. The kinetic performance of the electroless deposited Pt layers in the membrane was also examined and will be presented at the meeting.