Psychological factors, such as depression and anxiety, are independently associated with an increased risk of both diabetes mellitus and cardiovascular disease, but the reasons for these associations are unknown. We sought to determine whether psychological factors were associated with a greater prevalence of the metabolic syndrome in patients with coronary heart disease, and the extent to which such an association may be explained by socioeconomic status, health behaviors, and biological mediators. We conducted a cross-sectional study of 1024 outpatients with stable coronary heart disease. Psychological factors, including depressive and anxiety symptoms, hostility, anger, and optimism-pessimism, were assessed using validated standardized questionnaires. The presence or absence of the metabolic syndrome was determined using the criteria outlined by the National Cholesterol Education Program, Adult Treatment Panel III. Higher levels of depression, anger expression, hostility, and pessimism were significantly associated with increased prevalence of the metabolic syndrome. These associations were explained by differences in socioeconomic status and health behaviors. Additional adjustment for potential biological mediators had little impact. Further research is needed to determine whether addressing socioeconomic and behavioral factors in people with depression or high levels of anger or hostility could reduce the burden of the metabolic syndrome.