Abstract This paper investigates the influence of the inlet gas–liquid mixture non-uniformity on the performance of the TEB-type effervescent nozzle. The flow conditions studied are chosen to be relevant to industrial Fluid Coking operations. The investigation is limited to radial and vertical non-uniformities and conducted numerically by applying the mathematical model previously developed by the authors. The comprehensive mathematical model includes the liquid continuous flow through the variable cross-section nozzle, atomization, and spray dispersion. To quantify the inlet non-homogeneity, a new criterion related to the slope of the volume fraction inlet profile is proposed and utilized in the analysis. The simulations of a number of cases demonstrate that the inlet mixture radial non-uniformity does not produce substantial variations in the nozzle performance in terms of the spray quality. At the same time, the vertical non-uniformity can have a significant influence on the spray provided it is sufficiently strong. Further analysis reveals that the first convergent section of the TEB nozzle generates turbulence to facilitate phase mixing as the flow moves through the following divergent section. While this turbulence is sufficient for the flow with any radial non-uniformity and considered range of the inlet droplet diameter to completely eliminate the influence of the inlet conditions, it is not enough for the flow with moderate to strong degree of vertical non-uniformity.