Children's weight is a common reason for stigmatization. The aim of this study was to examine the effect of weight stigmatization (WS) during middle childhood on adolescent weight and the role of appetite self-regulation (ASR) as a potential mediator. Across three measurement time points, the study utilized a community sample of N = 1612 participants (51.9% female), aged 7-11 (T1), 9-13 (T2), and 16-21 (T3). WS was assessed via child-reports, different ASR facets (food responsiveness, emotional overeating, satiety responsiveness, external eating) via parent-reports, and height and weight were measured to calculate the standardized body mass index (BMI-SDS). Structural equation modeling was used to analyze the proposed prospective mediation. A total of 11.2% of the children reported WS experiences, with significant differences between the weight groups. ASR fully mediated the prospective association between WS and BMI-SDS. Higher WS predicted higher food responsiveness, higher emotional overeating, and, among older children, lower satiety responsiveness. Additionally, higher food responsiveness predicted higher adolescent BMI-SDS, indicating a specific indirect effect. The total indirect and specific indirect effects for food responsiveness remained significant when controlling for the established influences of parental BMI and body dissatisfaction. Our results highlight a prospective effect of WS on appetite self-regulation and propose ASR as a mediator for the association between WS and weight. WS and ASR might therefore be important factors for the prevention of overweight and obesity in children and adolescents.