To improve the sluggish oxygen reduction reaction from the cathode of solid oxide fuel cells (SOFCs), a conformal layer of catalytic CoO grains was deposited onto the internal surface of LSM/YSZ composite cathode of commercial cells, through atomic layer deposition (ALD). Upon the electrochemical operation, the ALD coated cell has dramatic reduction of the polarization resistance, and the power density exhibits continuous increase over the course of 172 h operation at 750 degrees C and reaches the cell performance enhancement by a factor of 1.6, in comparison with that from the baseline operated for 96 h. Such performance enhancement was attributed to the combination of the newly added triple phase boundaries for promoting the oxygen reduction reaction, as well as the accelerated oxygen transport on the cathode surface. The present work opens the further research direction for ALD coating of non-precious metal catalyst to boost the performance of as-fabricated SOFCs.