Background: Acute lymphoblastic leukemia (ALL) is the most common type of childhood cancer; Children with this type of leukemia have poor postural balance, which is one of the side effects of chemotherapy. Objective: Toevaluate the therapeutic effect of static and dynamic balance exercises using both sides up (BOSU) ball on balance in children with acute lymphoblastic leukemia after completing their 6 months-chemotherapy treatment. Patients and methods: Thirty children patients of both sexes (18 boys and 12 girls) were participated in this study, who were selected from Benha Children Hospital with acute lymphoblastic leukaemia and had chemotherapy treatment for 6 months participated in this study. They were randomly assigned to 2 groups of an equal number, control group, 15 child patients who were 5-8 years of age (6.53 ± 1.13) that underwent gait training therapy and study groups, 15 child patients who were 5-8 years of age (6.67 ± 1.11), that underwent the same program in addition to static and dynamic balance training program by using BOSU ball. Results: There was a significant improvement of balance performance in study group more than control group. Conclusion: Balance exercises using BOSU ball can be used effectively in treating balance defect post chemotherapy in children with acute lymphoblastic leukemia.