In this study, a mathematical model of liquid/liquid phase-transfer catalysis concerning mass transfer with reaction in a single organic droplet was developed. The diffusion resistance of an active phase-transfer catalyst in the organic phase and mass-transfer resistance between the droplet and the bulk aqueous phase were all considered. The film conversion parameter (phi) and mass Blot number of QY (Bi-QY) were defined to interpret their relative importance with respect to the organic reaction rate. Using this model, simulation results were consistent with the experimental data. From the simulation results, the organic phase reaction of QY with RX occurs mostly in the region close to the surface of the liquid droplet, depending on the film conversion parameter and the mass Blot number of QY. The reaction rate is influenced by the diffusion resistance as phi > 2, while the reaction rate is limited mainly by reaction and weakly by diffusion resistance as phi < 1. The amount of QY existing in the organic phase increases with increasing distribution coefficient of QY and mass-transfer coefficient from aqueous to organic phase, thus enhancing the overall reaction rate. The liquid/liquid phase-transfer catalysis can be well demonstrated by the present model.