Obesity prevention efforts in Aboriginal (First Nations, Métis, or Inuit) communities in Canada should focus predominantly on children given their demographic significance and the accelerated time course of occurrence of type 2 diabetes mellitus in the Aboriginal population. A socioecological model to address childhood obesity in Aboriginal populations would focus on the numerous environments at different times in childhood that influence weight status, including prenatal, sociocultural, family, and community environments. Importantly, for Aboriginal children, obesity interventions need to also be situated within the context of a history of colonization and inequities in the social determinants of health. This review therefore advocates for the inclusion of a historical perspective and a life-course approach to obesity prevention in Aboriginal children in addition to developing interventions around the socioecological framework. We emphasize that childhood obesity prevention efforts should focus on promoting maternal health behaviours before and during pregnancy, and on breastfeeding and good infant and child nutrition in the postpartum and early childhood development periods. Ameliorating food insecurity by focusing on improving the sociodemographic risk factors for it, such as increasing income and educational attainment, are essential. More research is required to understand and measure obesogenic Aboriginal environments, to examine how altering specific environments modifies the foods that children eat and the activities that they do, and to examine how restoring and rebuilding cultural continuity in Aboriginal communities modifies the many determinants of obesity. This research needs to be done with the full participation of Aboriginal communities as partners in the research.