Patients with pediatric acute lymphoblastic leukemia (ALL) experience rapid weight gain during treatment and increases in weight are maintained throughout treatment and beyond. Without prompt interventions, altered dietary and physical activity behaviors may become difficult to reverse, contributing to obesity risk long-term. Fifteen children, aged 3–9 years, diagnosed with pediatric ALL who were on maintenance therapy or within two years of treatment completion (mean BMI percentile: 70.4th) and one parent from each family, were enrolled into a 12-week lifestyle intervention delivered remotely through web-based sessions and phone calls with a lifestyle coach. Outcomes were assessed at baseline and end of the intervention. Thirteen of the 15 enrolled families (86.7%) completed the intervention. Parents reduced the “pressure to eat” feeding practice (change in mean score: −0.60, 95% CI: −1.12 to −0.07; p-value = 0.03) post intervention. Children increased the consumption of milk (0.54 serving/d, 0.02 to 1.07; p-value = 0.04) and percent of calories from protein (2.54%, 0.22 to 4.87%; p-value = 0.04) and reduced the consumption of potatoes (−0.16 serving/d, -0.30 to −0.03; p-value = 0.02). No significant changes were observed for children’s levels of physical activity, BMI, or waist circumference. Results from this pilot support the feasibility and preliminary efficacy of early lifestyle intervention among pediatric ALL survivors.