Obesity has been increasing in children and adolescents for decades. The reasons for this increase are not fully understood, despite research into factors such as diet, physical activity, and socioeconomic position. Psychosocial stress has been implicated as a social determinant for obesity. While psychosocial stress is understood as a multidimensional construct that operates at multiple levels and in different social contexts, the association between multiple forms of psychosocial stress and obesity among youth remains understudied, as well as the underlying mechanisms by which psychosocial stress may affect obesity. This study aims to define the relationship between multiple forms of psychosocial stress and obesity using longitudinal data from the Adolescent Brain Cognitive Development (ABCD) study, in order to increase the efficacy of prevention efforts and treatment to reduce obesity. The study will assess the association between different forms of psychosocial stress (neighborhood and interpersonal stress) and the growth trajectory of anthropometric outcomes (i.e., BMI and waist circumference), examine the role of psychosocial stress in explaining subgroup differences in anthropometric outcomes, investigate the extent to which obesity-related health behaviors mediates the relationship between psychosocial stress and adiposity, and evaluate the potential buffering effect of psychosocial resources (e.g., family support and positive school environment). Overall, this study has the potential to inform the optimization of existing clinical and place-based interventions aimed at reducing obesity by highlighting the importance of addressing psychosocial stress and identifying the context and most at-risk groups that can benefit from these interventions to reduce obesity.