In this work, we presents mass transfer model for three liquid phase transfer catalysis. The general model assumes that all chemical reactions are localized at phase interfaces. Despite this simplification, the predicted trends in conversion versus time and for variations of the model's dimensionless parameters are in accord with experimental observations. An analytical solution for conversion versus time is reported for the limiting case of a thin film of the third liquid phase separating an organic drop from the surrounding aqueous continuum. The analytical solution can be used to rationalize the observed jump in conversion upon formation of the third liquid phase and may assist in extracting kinetic information from experimental conversion data.