The impacts of the plant growth regulator, gibberellic acid (GA₃) were investigated on hemolymph free amino acids (FAAs) of Galleria mellonella L. (Lepidoptera: Pyralidae) larvae and its endoparasitoid Pimpla turionellae L. (Hymenoptera: Ichneumonidae) reared on host treated with different doses (50–5,000 ppm) of GA₃ in diet. High-performance liquid chromatographic analysis of the hemolymph revealed that out of the 20 amino acids detected, 18 FAAs were found in the hemolymph of treated and untreated host larvae, whereas 19 were present in that of parasitoid. The total pool of FAAs in host larvae after treatment by GA₃ fluctuated among doses and the ratio of essential amino acids in the pool increased to reach 9.54% at 1,000 ppm. Parasitoid larval total FAA concentration exhibited an increase at all treatments. However, the ratio of essential amino acids in the pool decreased >50% at all doses except for 50 ppm. Dose-dependent variations in individual FAAs in larval hemolymph of both species were also detected. Tyrosine, methionine, isoleucine, lysine, and tryptophan generally occurred in lowest amount both in control and treated G. mellonella larvae. The amount of serine, asparagine, glycine, isoleucine, leucine, and phenylalanine displayed differences only among GA₃ doses in treatments. Great variations in the amount of all amino acids occurred at most of the treatment doses in wasp larvae hemolymph. Our study indicated that application of GA₃ resulted in different effects on the quantity of FAAs associated with energy metabolisms of the pest species and its natural enemy.