Background: Treatment with chemotherapy markedly enhance remission rate in pediatrics leukemia. However, it is associated with various side effects (SEs) that can adversely affect the physical, emotional, and social well-being of pediatric patients. This study aims to assess the frequency and severity of chemotherapy-related SEs in pediatric leukemia patients at Benghazi Children's Hospital, Libya. Methods: A descriptive cross-sectional study was conducted from March to September 2023, involving 34 patients aged ≤12 years diagnosed with leukemia and receiving chemotherapy. Data were collected retrospectively from medical records, focusing on demographics, chemotherapy regimens, SEs, and laboratory results. The severity of SEs was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) Version 5. Results: Among the 34 patients, 55.9% were female, with a mean age of 5.9±3.1 years. Acute Lymphoblastic Leukemia (ALL) was diagnosed in 68% of cases. A total of 108 SEs were reported, averaging 3.17 episodes per patient. Neutropenia (21.3%) was the most common SE, followed by nausea and vomiting (12.0%). Severity assessment revealed that 48.1% of SEs were severe, and 22.2% were life-threatening. Conclusion: The study highlights the significant frequency and severity of chemotherapy-related SEs in pediatric leukemia patients, emphasizing the need for tailored monitoring and interventions to improve patient outcomes. Further research is warranted to develop effective preventive strategies...................... Keywords: ..............Childhood leukemia, chemotherapy, pediatric patients, Common Terminology Criteria for Adverse Events.