The performance characteristics of a rice husk based integrated gasification combined cycle (IGCC) plant has been developed at the variable operating conditions of gasifier. A thermo-chemical model developed by the authors has been applied for wet fuel (fuel with moisture) for predicting the gas composition, gas generation per kg of fuel, plant efficiency and power generation capacity, and NOx and CO2 emissions. The effect of the relative air fuel ratio (RAFR), steam fuel ratio (SFR), and gasifier pressure has been examined on the plant electrical efficiency, power output, and NOx and CO2 emissions of the plant with and without supplementary firing (SF) between gas turbine (GT) outlet and heat recovery steam generator (HRSG). The optimum working conditions for efficient running of the IGCC plant are 0.25 RAFR, 0.5 SFR, and 11 bar gasifier pressure at the GT inlet temperature of 1200 °C. The optimum operational conditions of the gasifier for maximum efficiency condition are different compared to maximum power condition. The current IGCC plant results 264.5 MW of electric power with the compressor air flow rate of 375 kg/s at the existed conventional combined cycle plant conditions (Srinivas et al., 2011, “Parametric Simulation of Combined Cycle Power Plant: A Case Study,” Int. J. Thermodyn. 14(1), pp. 29–36). The optimum compressor pressure ratio increases with increase in GT inlet temperature and decreases with addition of SF.