AbstractBackgroundAfter childhood acute lymphoblastic leukemia (ALL), sequelae include overweight and obesity, yet with conflicting evidence. We compared the prevalence of overweight and obesity between ≥5‐year ALL survivors from the North American Childhood Cancer Survivor Study (CCSS) and the Swiss Childhood Cancer Survivor Study (SCCSS) and described risk factors.MethodsWe included adult childhood ALL survivors diagnosed between 1976 and 1999. We matched CCSS participants (3:1) to SCCSS participants by sex and attained age. We calculated body mass index (BMI) from self‐reported height and weight for 1287 CCSS and 429 SCCSS participants; we then compared those with siblings (2034) in North America and Switzerland (678) siblings. We assessed risk factors for overweight (BMI 25–29.9 kg/m2) and obesity (≥30 kg/m2) using multinomial regression.ResultsWe found overweight and obesity significantly more common among survivors in North America when compared with survivors in Switzerland [overweight: 30%, 95% confidence interval (CI): 27–32 vs. 24%, 21–29; obesity: 29%, 27–32 vs. 7%, 5–10] and siblings (overweight: 30%, 27–32 vs. 25%, 22–29; obesity: 24%, 22–26 vs. 6%, 4–8). Survivors in North America [odds ratio (OR) = 1.24, 1.01–1.53] and Switzerland (1.27, 0.74–2.21) were slightly more often obese than siblings. Among survivors, risk factors for obesity included residency in North America (5.8, 3.7–9.0); male (1.7, 1.3–2.3); attained age (≥45 years: 5.1, 2.4–10.8); Non‐Hispanic Black (3.4, 1.6–7.0); low household income (2.3, 1.4–3.5); young age at diagnosis (1.6, 1.1–2.2). Cranial radiotherapy ≥18 Gray was only a risk factor for overweight (1.4, 1.0–1.8); steroids were not associated with overweight or obesity. Interaction tests found no evidence of difference in risk factors between cohorts.ConclusionsAlthough treatment‐related risk for overweight and obesity were similar between regions, higher prevalence among survivors in North America identifies important sociodemographic drivers for informing health policy and targeted intervention trials.