Anopheles stephensi with three different biotypes is a major vector of malaria in Asia. It breeds in a wide range of habitats. Therefore, safer and more sustainable methods are needed to control its immature stages rather than chemical pesticides. The larvicidal and antibacterial properties of the Pelargonium roseum essential oil (PREO) formulations were investigated against mysorensis and intermediate forms of An. stephensi in laboratory conditions. A series of nanoemulsions containing different amounts of PREO, equivalent to the calculated LC50 values for each An. stephensi form, and various quantities of surfactants and co-surfactants were developed. The physical and morphological properties of the most lethal formulations were also determined. PREO and its major components, i.e. citronellol (21.34%), L-menthone (6.41%), linalool (4.214%), and geraniol (2.19%), showed potent larvicidal activity against the studied mosquitoes.