Greater wax moth, Galleria mellonella L. is most commonly used as model insects for studying insecticidal efficiency of chemicals as well as it has been known as an alternative model to mamalian model for studying microbial infections and clinical drugs. The effects of a fluoroquinolone antibacterial agent, gemifloxacin, on sex ratio, male and female adult longevity, fecundity and hatchability of this insect were investigated by rearing the first instar larvae on artificial diets in the laboratory condition. The insect was reared from first-instar larvae to adult stage on an artificial diets containing gemifloxacin at 0.001, 0.01, 0.1 or 1.0%. Gemifloxacin did not affect male and female sex ratio and adult longevity while it significantly decreased egg number. Fecundity and hatchability were significantly and inversely decreased by increasing gemifloxacin concentrations. The females reared from control diet produced 134.46 per day, whereas high concentrations of gemifloxacin decreased the egg number to 26.75 and 53.5. Hatchability was also significantly decreased by 0.01% and above concentrations of gemifloxacin whereas, the highest concentration of antibiotic lowered the hatchability to 53.71%. This study indicated sublethal effects of gemifloxacin are likely to have a significant impact on adult biological traits and these effects show concentration-dependent variation in biological traits of the insect.