Although obesity is a chronic medical condition, not a psychological disorder, many researchers and clinicians agree that the psychological and social impact of living with obesity is a risk factor in the development and persistence of mental health problems. In adults with mental health disorders, the prevalence of obesity is nearly twice as high as compared to adults without mental health disorders. The research evidence supports the predictive relationship of child emotional and behavioral problems (e.g., high levels of internalizing and externalizing behaviors) and the later life development of obesity or overweight. About 80% of adolescents with obesity will continue to be obese as adults. Psychological and social comorbidities associated with excess body weight in childhood and adolescence includes anxiety, depression, poor body image and self-esteem, and decreased social competence and academic achievement. This chapter discusses the assessment and management of obesity.