This theoretical review develops weight self-concept (perception of one’s body as thin/overweight) as a dimension of self-concept and distinguishes it from body image (affective evaluation of one’s body) which is a dimension of self-esteem. It proposes that weight self-concept and body image might resemble other dimensions of self-concept and self-esteem in that they coalesce after the instability of adolescence and are thereafter resistant to change. Therefore, in considering the determinants of weight self-concept and body image this paper reviews the literature on those aspects of the adolescent experience which influence weight self-concept and body image, particularly pubertal timing. This paper also addresses the implications that weight self-concept might have for understanding identity formation and identification with stigmatized groups (such as overweight). The conclusion discusses the importance of interventions during pre-adolescence to prevent the development of a stigmatized, overweight self-concept and negative body image.