Liquid-liquid-liquid equilibrium (LLLE) data are reported for the water + benzene + caprolactam + ammonium sulfate system at 293.1 K, 313.1 K, and 328.1 K. The experiments show a distinct pattern of phase behavior with increasing salt concentration and temperature. The tricritical point of the system was not determined, but was estimated to be around 332 K The results are modeled using a modification of the extended electrolyte NRTL model. The model was able to represent the LLLE data satisfactorily.