This article presents findings from a study that evaluated the utility of Protection Motivation Theory to explain cardiovascular health behaviors among people with schizophrenia (n = 83) and depression (n = 70). Results indicated that the prevalence of overweight, cigarette smoking and a sedentary lifestyle were greater among people with a mental illness compared to individuals without a mental illness. Major predictors were high levels of fear of cardiovascular disease, lack of knowledge of correct dietary principles, lower self-efficacy, limited social support and psychiatric symptoms. Implications of these results are discussed in designing education and preventive health programs for individuals with schizophrenia and Mental Depressive Disorder (MDD).