Reaction races and surface activities for synthesis of an ether-ester by liquid-liquid phase transfer catalysis were qualitatively correlated at 298 K. The surface activity was obtained from surface pressure data and the reaction rate was measured using a Lewis-type stirred cell. All experiments were performed as a function of the concentrations of aqueous-phase reactant (a substituted phenylacetic acid), phase transfer catalyst, alkali, and organic-phase reactant (a haloalkane). The same tendencies for surface activity and reaction rate were observed. This study allowed us to predict the trends of reactivity at different conditions simply from interfacial tension measurements.