In this study, an equilibrium model for NOx emission in gas turbine combustors was developed. The model is based on the governing thermodynamic, materials, and energy balance equations. Results obtained from the model simulation were compared with operational data from a local gas turbine power plant. There was about a 3 to 6 percent deviation for the periods considered. Consequently, the model is reliable in the design of new combustors and in assessing the pollutant emission during operations. It was established that factors that affect NOx formation include flame temperature and quantity of excess air used. Furthermore, the results revealed that the most important parameter that governs the formation of NOx is flame temperature, as the formation of NOx rises exponentially with an increase in the combustor flame temperature.