The use of semiochemicals as repellents and attractants has been proposed to complement insecticides used for the control of vector mosquito populations. In several studies, the optical purities of the molecules tested have been described as having little or no effect on repellent activity. However, these observations seem difficult to explain because of the chirality effect of molecules on the olfactory system of insects and humans. Thus, the purpose of this study is to assess the effects of chirality on the repellent properties of 4-alcoxycoumarins against Aedes albopictus Skuse, mosquito vector of arboviruses. We report here that the racemic (R/S)-4sec-butoxycoumarin had the highest repellent effect (Repellent Index = 49.9%) followed by (R) enantiomer (Repellent Index = 24.2%) for the dose of 5 mg/mL. Contrary, no significant repellent activity was recorded for S-(+)-4-sec-butoxycoumarin. This experiment demonstrates the close relationship between the molecules' optical purities and the behavioral response of mosquitoes.