Objective: This study identified the associations between the AeRop exercise (Indonesian abbreviation of a technique combining aerobic exercise with progressive muscle relaxation) and the sleep quality and fatigue of pediatric cancer patients undergoing chemotherapy. Method: This quasi-experimental with control group study evaluated the AeRop exercise in 64 children with cancer undergoing chemotherapy who were recruited through a consecutive sampling method. They were assigned to intervention and control groups. Their fatigue and sleep problems were measured on day 1 and day 5 using Allen's Fatigue in Childhood Fatigue Scale and Sleep Disturbance Scale for Children. The data were analyzed using univariate analyses, dependent t-tests, and independent t-tests. Results: There was a statistically significant difference in the sleep problems between the two groups after the AeRop exercise. However, the fatigue levels between the groups were only found to be slightly different (p = 0.05). Conclusion: The AeRop exercise was associated with lesser sleep problems in the pediatric patients undergoing chemotherapy. This type of light exercise can be implemented as a nursing intervention in order to improve sleep in children with cancer.