This paper presents the computational study carried out on an aero gas turbine combustor to assess important performance parameters. The CFD results are compared with experimental data obtained from the full scale combustor tested at ground test stand simulating various operational conditions. The CFD predictions have agreed well with the experimental data. The model is then used to predict combustor exit temperature pattern factors, pressure loss, and combustion efficiency and exhaust gas constituents over a wide range of ambient temperatures at ISA sea level conditions to study their effect on performance parameters. The exhaust gas temperature is found to increase with increase in ambient temperature but the radial and circumferential pattern factors are found to be less at higher temperature and more at lower temperatures. Pressure loss is also increases at lower temperatures but combustion efficiency increases with increase in temperature. The findings of this study are valuable inputs for engine performance estimation at any regional climatic condition.