In this study, the biological effects of the ethephon (ETF), which is an organic phosphorus and ethylene generating commercial compound, were determined on the model organism, the greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae). The median lethal dose (LD50) of ethephon were determined in the larval stage, incorporating into artificial diets at concentrations of 48, 96, 144, 192, 240, 384, 408, and 432 mg/ml using probit analysis. The larval-pupal weights, larval and pupal developmental time and adult longevity were examined over the treatments. The LD50 doses of ethephon was determined as 353.53 mg/ml. All doses of ETF treatments caused significant decreases in the developmental time of larval and pupal stages and adult longevity of model organism G. mellonella. The larval-pupal weights also decreased in all treatments when compared with untreated control. Our work showed that ETF has detrimental effects on biological fitness of insects and future studies should aim to determine the ecophysiological mechanisms of toxicity.