Ag@Pt nanoparticles synthesized with different Ag/Pt mass ratios utilizing ultrasonic treatment method. These materials were supported on Vulcan XC-72 and utilized as cathode in a proton exchange membrane fuel cell (PEMFC). The morphology of this material characterized through the x-ray diffraction (XRD), induced coupled plasma atomic emission spectroscopy (ICP-OES) as well as; high resolution transmission electron microscopy (HRTEM) techniques. To begin with, it was proven that, the prepared Ag@Pt/C catalyst possessed a core-shell nanostructure. The electrochemical properties of this material investigated through the Cyclic Voltammetry (CV), linear sweep voltammetry (LSV) and Electrochemical Impedance Spectroscopy (EIS) in acidic media. Moreover; it was shown that, the Ag@Pt/C with Ag/Pt ratio of 1:3 possessed the largest electrochemical surface area (ESCA) of 67.8 m(2) g(-1) and its oxygen reduction activity proceeded through a 4e(-) reaction pathway. Furthermore; it was demonstrated that, the determined stability of the (1:3) Ag@Pt/C was significantly higher compared with those of other elctrocatalysts prepared at different Ag/Pt ratios in particular; to the one without the Ag element (i.e.; a commercial Pt/C one). Ultimately, the electrocatalytic behavior of the (1:3) Ag@Pt/C) investigated through a unit cell structure of a PEMFC and compared with that of a virgin commercial Pt/C cathode. It was observed that, the maximum power density of the MEA utilizing the (1:3) Ag@Pt/C electrocatalyst was 30% higher than that of the Pt/C. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.