Objective: Mental disorders are among the leading causes of disability in the United States. In 2011, over 10 million adults felt that even though they needed treatment for mental health problems, they received insufficient or no mental health care and reported unmet need. This article assesses associations between sociodemographic characteristics and perceived causes of unmet needs for mental health care. Method: A sample of 2,564 adults with unmet mental health need was obtained from the National Survey on Drug Use and Health. Outcome variables were 5 main reasons for unmet need: cost, stigma, minimization, low perceived treatment effectiveness, and structural barriers. Each cause of unmet need was regressed on sociodemographic, health, and service use characteristics. Women had higher odds of cost-related reasons for unmet need than men. Odds of stigma and structural barriers were greater among Blacks than Whites, and among rural than metropolitan residents. Compared with the uninsured, insured persons were less likely to report cost barriers. However, insured persons had higher odds of stigma and minimization of mental disorders. Conclusions and Implications for Practice: Insurance alone is unlikely to resolve the problem of unmet need. Understanding the social epidemiology of perceived unmet need will help identify populations at risk of not receiving mental health care or insufficient care. Focusing on specific programs and services that are designed to address the causes of perceived unmet need in particular populations is important. Future research should explore how intersecting social statuses affect the likelihood of perceived unmet need.