OBJECTIVE: This study evaluated the relation among weight-based stigmatization, ideological beliefs about weight, and psychological functioning in an obese, treatment-seeking sample. RESEARCH METHODS AND PROCEDURE: Ninety-three obese, treatment-seeking adults (24 men and 69 women) completed a battery of self-report questionnaires measuring psychological adjustment, attitudes about weight, belief in the controllability of weight, and the frequency of weight-based stigmatization. RESULTS: Weight-based stigmatization was a common experience for participants. Frequency of stigmatizing experiences was positively associated with depression, general psychiatric symptoms, and body image disturbance, and negatively associated with self-esteem. Further, participants' own negative attitudes about weight problems were associated with their psychological distress and moderated the relation between the experience of stigmatization and body image. DISCUSSION: Weight-based stigmatization is a common experience for obese individuals seeking weight loss treatment and appears to contribute to poor mental health adjustment. The negative effects of these experiences are particularly damaging for those who hold strong antifat beliefs.