We developed a nano-structured Sm0.5Sr0.5CoO3 (SSC55) cathode from slurry dispersed nanoparticles using a planetary bead-milling method. In order to evaluate the cathode performance, the cathode resistances and the protonic ceramic fuel cell properties were examined using electrochemical cells with a BaCe0.6Zr0.2Y0.2O3 - delta electrolyte disk at intermediate temperatures. The cells with a milled SSC55 cathode showed lower cathode resistance and higher power density compared to those with the SSC55 cathode prepared from the conventional method. The improvement is attributed to an increase in the cathode reaction sites caused by the use of the smaller particles and a good adhesion to the electrolyte surface. (C) 2013 Published by Elsevier B.V.