Infiltrating fine-grained electrocatalyst particles of either ion conducting or mixed electron and ion conducting (MEIC) material into a ceramic porous electrode scaffold has proven a very effective way to improve electrode performance for low to intermediate temperature solid oxide fuel cells (SOFCs). We report here one-step infiltration of MEIC fine particles, La0.6Sr0.4CoO3-delta (LSCo) and SrCo0.8Fe0.2O3-delta (SCF), into a commercial cathode substrate. A comparative study shows that the cathode polarization can be considerably reduced by a factor of 17 to 28 and 28 to 49 from 1000 to 700 degrees C by the infiltrated LSCF and SCF electrocatalysts, respectively, demonstrating an effective solution to improve the electrode performance without altering mechanical properties of the electrode substrate. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.007201esl] All rights reserved.