The effects of carrier gas flow rates and Boudouard reaction on the performance of Ni/YSZ anode-supported solid oxide fuel cells (SOFCs) have been studied with coconut coke fuels at 800 °C. Decreasing flow rates of carrier gas from 1000 to 50 ml min−1 increased open circuit voltages and current densities from 0.71 to 0.87 V and from 0.12 to 0.34 A cm−2, respectively. The increased cell performance was attributed to the increasing extent of electrochemical oxidation of CO, a product of Boudouard reaction. The contribution of CO oxidation to current generation was estimated to 66% in flowing inert carrier gas at 50 ml min−1. The pulse transient studies confirmed the effect of flow rates on cell performance and also revealed that CO and CO2 can displace adsorbed hydrogen on carbon fuels. Flowing CO2 over coconut coke fuel produced CO via Boudouard reaction. The presence of CO led to a highest power density of 95 mW cm−2, followed by a concurrent decline of power density and CO concentration. The declined power density along with decreasing CO concentration further verified contribution of gaseous CO to the power generation of C-SOFC; the decreasing CO concentration showed a typical kinetics behavior of Boudouard reaction, suggesting the loss of active sites on carbon surface for the reaction.