In this work, the performance of solid oxide fuel cells (SOFCs) fed with a syngas obtained from a steam-enriched air gasification of biomass has been investigated, varying the composition of the feeding gas (H2, CO, CO2, CH4, H2O, and N2). The composition has been obtained from experimental/numerical tests in a fluidized bed bench scale gasifier after catalytic steam reforming of the syngas carried out to remove tar. During the gasification tests, the oxygen purity in the enriched air (in the range of 0.2 and 0.9), the gasification process temperature (in the range of 750 and 850 °C), the steam to biomass (in the range of 0.5 and 1) and the equivalence ratio (in the range between 0.0 and 0.4) were varied to simulate the different operating conditions. Commercial SOFC cells have been employed in the experimental campaign, fed with the most representative fuel compositions mentioned above. Polarization curves have been carried out to determine the electrical performance of the cells, comparing the results with cells fed with hydrogen only. In the final paper, the electrochemical impedance spectroscopy (EIS) will be reported for in-depth analysis of the performance parameters and to evaluate the long term degradation rate of the cell.