Background: Obesity has become a serious problem threatening the health of children and adolescents, and China's one-child policy has affected family structure and parenting practice, which may result in several adverse health outcomes. The present study aims to investigate the association between single-child status and the risk of abdominal obesity in Chinese adolescents and also to compare the differences in the risk of unideal energy-related behaviors.Methods: Data were obtained from a school-based cross-sectional survey conducted in seven provinces of China, in 2012. A total of 31,291 students aged 7–17 years were recruited in this study. Anthropometric measurements were conducted to assess height and waist circumference, and questionnaires were used to obtain information of single-child status, parental educational attainment, parental weight status, and offspring energy-related behaviors. Multivariate logistic regression models were used to estimate the odds ratio (OR) and 95% confidence intervals (95% CI) of single-child status and odds of childhood abdominal obesity and energy-related behaviors.Results: The prevalence of abdominal obesity was 18.2% in single children, which was higher than that of non-single children (13.7%). The prevalence was also higher in single children in different sex and residence subgroups. Logistic regression models showed that single children had 1.33 times (OR: 1.33, 95% CI: 1.24–1.43, P < 0.001) higher odds of abdominal obesity compared to non-single children. Single children had 1.08 times higher odds of physical inactivity (OR: 1.08, 95% CI: 1.03–1.14, P = 0.004), 1.13 times higher odds of excessive sugar-sweetened beverages (SSBs) consumption (OR: 1.13, 95% CI: 1.05–1.23, P = 0.002), and 1.08 times more likely to eat out (OR: 1.08, 95% CI: 1.02–1.13, P = 0.006). Those associations were more remarkable in single girls.Conclusion: Being a single child may be associated with a higher odds of childhood abdominal obesity and unhealthy energy-related behaviors. Future interventions and strategies to prevent abdominal obesity should focus on this high-risk population.