This study experimentally analyzes the performance and degradation issues of an anode supported (AS) Ni-YSZ solid oxide fuel cell exposed to thiophene (C4H4S). The impact of this organic sulfur compound on the performance of SOFC Ni-YSZ anodes is reported as a function of temperature and the impurity concentration. There are extensive investigations on the effect of hydrogen sulfide as inorganic sulfur compound on the performance of SOFC but much less of complex sulfur-containing molecules like thiophene. The main objective of this study is to evaluate the impact of thiophene at constant (5 ppmv) and variable (1-15 ppmv) concentrations in the fuel stream on the SOFC performance and regeneration. With the help of the observed results on polarization with time and impedance spectroscopy, including the use of a new equivalent gas composition of reformed bio-syngas, the degradation mechanism is explained. Post-test characterization (SEM-EDX) helps to clarify carbon formation and degradation due to the sulfur impurity. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.