In this study, we determined the effects of a meridic diet on adult emergence, glycogen and protein level of the endoparasitoid Pimpla turionellae, and investigated female lifetime, adult emergence rate, egg numbers and hatching for five generations. The meridic and control diets were fed to P. turionellae for 28 days. The meridic diet was associated with a significant increase in the total adult emergence, which reached 93.33% on day 16; 100% females were produced from eggs laid on day 25. The meridic diet significantly decreased glycogen level in P turionellae on days 13 and 16, while it significantly increased the protein level on days 13, 16 and 19 in comparison to the control natural diet. The meridic diet did not negatively affect total adult emergence, lifetime and egg numbers over the first and second generations when compared to the control. However, female lifetime and egg numbers were significantly decreased in F3, F4 and F5 generations. This manuscript is the first to report rearing the adult stages of P. turionellae on meridic diets for five generations. It shows that a chemically-defined meridic diet may be beneficial in improving the biological and biochemical fitness of the first couple of generations of these parasitoids reared for use in biological control programs.