An aphid parasitoid, Aphelinus basilicus Fatima & Hayat (Aphelinidae: Aphelininae) is described from material collected in Bengaluru, Karnataka for the first time. It was found to parasitize apterous viviparous females of the cotton aphid, Aphis gossypii (Glover) infesting Gossypium hirsutum (Malvaceae), during Jul, 2013. Field data indicated that the parasitoid, Aphelinus basilicus parasitized dark green forms (88%) of A. gossypii more frequently than pale green (24%) and yellow forms (2%) suggesting that the body color strongly influenced the host preference for foraging. The 3 color forms were differentially susceptible to selection by the parasitoid. Statistical analysis revealed that the parasitoid had an inherent preference for dark green forms (P < 0.05). Information on the parasitoid's distribution, diagnostic characters, host range and host preference are presented to ease the identification as well as to understand the fundamentals of host selection behavior of this species. This is a new distributional record of Aphelinus basilicus parasitizing color forms of A. gossypii associated with G. hirsutum in Karnataka, India.