The self-emulsification of oils containing dissolved solutes is not only an intriguing phenomenon but is also of practical interest in the delivery of agricultural chemicals and drugs. Herein, a facile one-step self-emulsification of eugenol with tunable release rates of encapsulated lipophilic compounds was enabled simply by gently mixing eugenol with modified rice proteins (MRPs). Due to binding with eugenol by hydrophobic interactions lowering the oil/water interfacial tension, MRPs underwent secondary structure changes and precipitated on eugenol droplets of nanoscale. Increasing the MRP : eugenol ratio enabled the formation of more porous interfacial films to increase the first-order release rate of eugenol and the resultant anti-proliferation activity of encapsulated caffeic acid phenethyl ester (CAPE) against HTC-116 human colorectal cancer cells. Therefore, novel emulsions with varied interfacial structures can be fabricated utilizing MRPs to control release characteristics and bioactivity of lipophilic compounds.