We report on single phase polycrystalline Ba0.5Sr0.5Co0.8Fe0.2O3 thin films grown on (1 0 0) (Y2O3)(0.08)(ZrO2)(0.92) substrates by radio frequency sputtering. Detailed studies on electrical conductivity as a function of temperature up to 500 degrees C are carried out for films in the 20-100 nm thickness range. Free-standing thin film micro-solid oxide fuel cells utilizing nanostructured Ba0.5Sr0.5Co0.5Fe0.2O3 cathodes are fabricated and tested for the first time. A maximum power density of 35 mW cm(-2) at 520 degrees C was obtained with Ba0.5Sr0.5Co0.5Fe0.2O3/(Y2O3)(0.08)(ZrO2)(0.92)/Pt micro-solid oxide fuel cells. These results indicate the significance of microstructure on electrical properties of Ba0.5Sr0.5Co0.8Fe0.2O3 and present the first successful thin film micro-solid oxide fuel cells integrating Ba0.5Sr0.5Co0.8Fe0.2O3. We anticipate these results to be of relevance in advancing micro-solid oxide fuel cells for reduced temperature operation with dense oxide cathodes. (C) 2011 Elsevier B.V. All rights reserved.