In the enantioselective esterification of racemic naproxen with 4-(2-hydroxyethyl) morpholine by Lipase MY in organic solvents, a productivity improvement of the desired (S)-naproxen ester from 0.42 to 0.72 mM at the reaction time of 130 h was observed, when the surfactant bis (2-ethylhexyl) sodium sulfosuccinate (AOT) was added in the reaction mixture. The presence of a small amount of exogenously added water dramatically activated the enzyme in AOT/cyclohexane-reversed micelles. Desorption of the surfactant molecule from the enzyme mass and solubilization of the enzyme into reversed micelles were used to elucidate an existing maximum of the initial rate of (S)-naproxen synthesis with the water content. Moreover, the effects of alcohol and surfactant concentration on the enzyme activity are reported.