We examined the stage and sex-related changes in total lipid, total fatty acids, and fatty acid composition of Apanteles galleriae Wilkinson (Hymenoptera: Braconidae) reared on Achoria grisella Fabr. (Lepidoptera: Pyralidae). The effect of parasitism on the total lipid and fatty acids of host larvae was also investigated and compared with the fatty acid composition of parasitoids. The changes in fatty acid composition of host larvae after parasitization were investigated and the degree of similarity between the fatty acid composition of parasitoid and host larvae was determined. Total lipid of A. galleriae considerably increased in adults compared with immature stages. There was a significant increase in fatty acid levels between the larval and pupal stages. Fatty acids continued to accumulate in adult males, but declined in females. Total fatty acids of parasitoid larvae were significantly higher than that of parasitized or nonparasitized host larvae. All stages of A. galleriae contained the 10–24 carbon fatty acids. Oleic acid was the most abundant fatty acid in all stages. A large proportion of the fatty acid composition at each developmental stage of the wasp analyzed comprised palmitic, palmitoleic, stearic, oleic, linoleic, and linolenic acids. The fatty acid composition of the parasitoid larvae was qualitatively similar to that of the host larvae. Parasitism did not affect the total lipid and fatty acid levels of host larvae.