A Gd-doped ceria (GDC) buff er layer is required between a conventional yttria-stabilized zirconia (YSZ) electrolyte and a La-Sr-Co-Fe-O3 (LSCF) cathode to prevent their chemical reaction. In this study, the eff ect of varying the conditions for fabricating the GDC buff er layer, such as sintering temperature and amount of sintering aid, on the solid oxide fuel cell (SOFC) performance was investigated. A finer GDC powder (i.e., ultra-high surface area), a higher sintering temperature (～1290℃), and a larger amount of sintering aid (～12%) resulted in improved densification of the buff er layer; however, the electrochemical performance of an anode-supported cell containing this GDC buff er layer was poor. These conflicting results are attributed to the formation of (Zr, Ce)O2 and/or excess cobalt grain boundaries (GBs) at higher sintering temperatures with a large amount of sintering aid (i.e., cobalt oxide). A cell comprising of a cobalt-free GDC buff er layer, which was fabricated using a low-temperature process, had lower cell resistance and higher stability. The results indicate that electrochemical performance and stability of SOFCs strongly depend on fabrication conditions for the GDC buff er layer.