For the first time, we report here the synthesis and use of pentyl and cetyl rhamnoside as cosurfactant or surfactant, respectively, and their evaluation in cosmetic formulations. l-rhamnose is more reactive than d-glucose in direct acetalization with long alkyl chains of alcohol, because of its higher lipophilicity, whereas for short alkyl chains, glucose and rhamnose are equivalent. Furthermore, pentyl rhamnoside could be used as a new non-toxic cosurfactant to formulate microemulsions. Finally, a white continuous aqueous phase emulsion and a liquid soap were evaluated for cosmetic uses. These new formulations showed very good cosmetic properties with high hydration properties and rapid cutaneous penetration.