In this article, it was demonstrated the use of ultrasound technique to synthesize the platinum-cobalt electrocatalyst supported on carbon-encapsulated polyaniline (Pt-Co/C-PANI). The ultrasound-assisted cavitation technique provides a uniform dispersion of Pt and Co nanoparticles onto the carbon and polyaniline support. Nanoparticles of Pt-Co/C-PANI exhibited spherical morphology and the particle size ranging from 10 to 20 run. A membrane electrode assembly (MEA) was prepared using as-synthesized electrocatalysts; Oxygen reduction reaction (ORR) activity and the cell voltage was evaluated in a polymer electrolyte membrane (PEM) fuel cell. The Pt-Co/C-PANI electrode exhibited open circuit potential (OCP) of 0.91 V and electrochemical active surface area (EASA) was found to be 5.98 m(2)/g. The electrocatalyst provided a maximum current density of 120.8 mA/cm(2) at 0.29 V and maximum power density of 36.4 mW/cm(2) at 0.37 V.