Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, accounting for 25% of all childhood malignancies. Treatment of childhood ALL has a high success rate, with long-term event-free survival of >85%. Treatment success, however, has not come without cost. Recognition of long-term health problems related to childhood cancer therapies is growing. Both during and after therapy, children treated for ALL are at risk for fatigue, reduced physical activity, poor dietary intake, and excessive weight gain, which are driven by physiological (chemotherapy-induced) changes and social (home/environmental) factors. The goals of this pilot study are to evaluate the feasibility, acceptability, and potential efficacy of a parent-targeted, phone-delivered nutrition and physical activity program to prevent unhealthy weight gain among 60 childhood ALL survivors, 4-10 years of age. Participants will be randomly assigned to either the phone-delivered parent-targeted nutrition and physical activity intervention or a standard-of-care control group. Intervention success will be benchmarked by changes in key weight-related behaviors (physical activity and dietary intake) over the 6-month trial, and initial impact of the intervention on biomarkers of inflammation and oxidative stress, fatigue, and body composition will be examined.