Phenol (PN), obtained from coal tar, is used commonly in medical treatments, industrial areas, petroleum refineries, production of glue, fiber, and nylon. PN is used in the production of benzene and it is emitted in the atmosphere by motor vehicles. Folic acid (FA) is an essential nutrient among the B complex group of vitamins. The main aim of this study was to investigate the effects of PN and PN + FA on various developmental stages of Drosophila melanogaster. Different concentrations of PN and PN + FA were administered during the developmental periods of the fly (egg, larva and pupa). When F1 progeny of control and experimental groups were compared, PN was found to extend the process of metamorphosis and decrease the total offspring numbers. However, these negative effects were inhibited by FA treatment at different concentrations (0.25-2.50 mg/kg). These results suggest that FA could effectively inhibit PN-induced abnormalities in developmental stages of Drosophila melanogaster.