Parasitic infections present a significant clinical challenge for cancer patients, particularly in recent years as advances in chemotherapy have led to an increase in immunosuppressed individuals (Wassef R, Rizk E, Abdel-Malek R, Open Forum Infect Dis 3:582, 2016). While many parasitic infections remain asymptomatic, their potential to cause severe and sometimes fatal complications in immunocompromised hosts necessitates vigilant screening protocols prior to initiating cancer therapy. It is essential for clinicians to be familiar with the epidemiology, most prevalent species, clinical manifestations, diagnostic approaches, and treatment strategies associated with these infections. Intestinal parasitic diseases constitute a global public health concern, with an estimated 1.5 billion cases reported worldwide (Singh B, Dhakal P, Parajuli RP, J Parasit Dis 48(1):46–52, 2024)—predominantly affecting populations in developing countries. Among cancer patients, intestinal parasites may be responsible for secondary diarrhea, a symptom often otherwise attributed to the adverse effects of chemotherapy, particularly in individuals with leukemia. Given the potential for these infections to complicate cancer management, a thorough understanding is required not only to ensure optimal patient outcomes but also to guide appropriate preventative measures. This chapter will provide an in-depth overview of the most commonly encountered parasitic infections in cancer patients, emphasizing their clinical significance, modes of transmission, diagnostic challenges, and evidence-based treatment protocols. Through a comprehensive review of current literature and clinical data, we aim to equip healthcare professionals with the knowledge necessary to identify and manage parasitic infections in the oncology setting, thereby improving both patient safety and quality of care.