Concerns over the ecological impacts of insecticides have led researchers to look for environmentally friendly plant-derived pest control compounds such as plant growth regulators. Here we investigate whether the plant growth regulator abscisic acid (ABA) alters the life history traits and hemocytes of Galleria mellonella L. (Lepidoptera: Pyralidae) when injected into the hemocoel. The injection of ABA resulted in dose-dependent mortality of final-instar larvae, as well as an increase in the duration of the larval stage and adult emergence time, and decrease in pupation and adult emergence ratios. The mean adult longevity and fecundity of G. mellonella adults was lower at higher doses. Injection of different concentrations of ABA led to a remarkable decrease in the number of circulating hemocytes at all time intervals. Analyses of the differential hemocyte counts revealed that ABA altered the granulocyte and plasmatocyte ratio in a dose-dependent manner at different time intervals. The percentage of mitotic hemocytes also decreased at 10 and 50 mg/ml at 24 h post ABA injection. These findings demonstrate that ABA may interfere with development and the hemocytes of G. mellonella and could be a good candidate for pest control after detailed study of ingestion and contact effects in further studies.