Introduction: Acute leukemia is the most common form of childhood cancer and is the primary cause of cancer-related mortality in children.

Material and methods: Complete blood count investigations were done to patients with acute leukemia and healthy control by manual method.

Results: A significant decrease in hematological parameters as total leucocytes count, hemoglobin, Red blood cell count, platelets count, hematocrit and neutrophils percent during chemotherapy compared to before chemotherapy as action of chemotherapy.

Conclusion: This study proved that children with acute leukemia suffered from leucopenia, anemia, and thrombocytopenia during chemotherapy that made them susceptible to infections and bleeding complications.