Alternative animal models have become increasingly necessary due to legal regulations aimed at reducing the use of laboratory animals. Invertebrates are gaining in importance and have been intensively researched in recent years due to their pathophysiological similarities with rodents. Among these organisms, Tenebrio molitor, also known as the yellow mealworm beetle, stands out. In this study, we investigated whether T. molitor could be an alternative for studying the toxicity of chemotherapeutic agents. For this purpose, T. molitor larvae were inoculated with irinotecan (IRI) or 5-fluorouracil (5-FU). Both chemotherapeutic agents increased the morbidity and mortality of T. molitor and led to an increase in total circulating cells. Glucose levels were decreased after treatment with 5-FU and alanine aminotransferase levels were decreased after IRI administration. Administration of IRI or 5-FU resulted in changes in the appearance, consistency and amount of T. molitor frass. Finally, both IRI and 5-FU promoted severe histologic damage in the midgut and increased melanin deposition in peripheral tissues. Finally, we succeeded in developing an alternative experimental model for evaluating the toxicity of IRI and 5-FU. This model exhibits significant features of toxicity and intestinal damage, making it suitable for translational research purposes. T. molitor proves to be a versatile model organism with numerous advantages for experimental studies and offers a viable alternative for acquiring and expanding knowledge in the field of toxicology and pharmacology.