This study numerically analyzed NOx emissions for pentane spray combustion. Thermal and prompt pathways are used to model NOx formation under the equilibrium oxygen condition and the OH exclusion model. The k-ε model analyses the turbulent flow field, and the mixture fraction-probability density function model is used to construct the combustion model. The most important parameters studied are temperature, OH, CO, mass fractions of NOx, and NOx generation rates. The results show that prompt NOx processes produce substantially higher emissions compared to thermal mechanisms. The combined models (prompt and thermal) exhibit a variation of approximately 1% in NOx mass fractions and their generated rates. The results indicate that the thermal model is better than the prompt model in all the domains studied, especially in reducing nitrogen oxide emissions.