The current study investigated the relationship between just world beliefs and stigmatizing attitudes toward eating disorders and obesity. Further, the associations between stigma and causal beliefs, and between stigma and acquaintance with these conditions, were examined. Participants (n = 447) read four vignettes describing an individual with anorexia nervosa, bulimia nervosa, binge eating disorder, or obesity. After each vignette, participants completed questionnaires assessing stigmatizing attitudes, just world beliefs, causal beliefs, and acquaintance with the condition depicted in the vignette. Stronger just world beliefs were associated with greater stigma toward all three eating disorders, as well as obesity (rs ranging from −.11 to −.18). More stigmatizing attitudes were associated with greater attribution of individual responsibility for the development of the disorder. However, participants with personal experience or who knew someone with the depicted problem did not have lower stigma scores than those who did not. The current study suggests that justification ideologies such as just world beliefs and controllability beliefs may underlie the stigmatization of eating disorders and obesity. These findings provide support for stigma reduction efforts aimed at targeting justification ideologies and altering causal beliefs.