Society’s emphasis on a thin body ideal may intensify an individual’s negative perceptions of fatness. The purpose of the present study was to examine the relationship between sociocultural attitudes toward appearance (awareness and internalization of the female ideal) and anti-fat attitudes among middle-aged Korean women. In addition, the aim was to examine whether the body internalization of female ideals was a mediator in the proposed model. Participants included a sample of 264 middle-aged Korean women who completed a series of measures online. The following information was collected through online questionnaires: awareness and internalization of the female ideal, attitudes toward fat, body weight perception, and demographics. Data were analyzed using correlation analysis, descriptive analysis, factor analysis, and structural equation modeling. The measurement model and the structural model testing provided an acceptable fit to the data, and all proposed pathways in the research model were statistically significant. Awareness of the female ideal was significantly and positively associated with internalization, and it significantly and positively predicted both constructs of anti-fat attitudes. Additionally, awareness of the female ideal was significantly and positively indirectly associated with attitudes toward fat peopledislike and willpower mediated by internalization. Overall, these findings suggest that society’s emphasis on female appearance and a thin body can ultimately result in significant stigmatization of overweight/obese individuals. This study emphasizes the importance of establishing a healthy appearance standard to reduce anti-fat prejudice.