Objective: Medication nonadherence presents a considerable problem in patients with schizophrenia. There are limited and conflicting data on the association of cognitive impairment with antipsychotic nonadherence. In this study, we evaluated the correlation of patients' scores on Mattis' Dementia Rating Scale (DRS; total and subscale scores) with scores on the Medication Management Ability Assessment (MMAA), a performance-based measure of medication management. Methods: Participants included 110 outpatients with schizophrenia or schizoaffective disorder. Each was evaluated using the MMAA role-play tasks and the DRS. Patients also completed the Drug Attitude Inventory (DAI), and the PANSS (Positive And Negative Syndrome Scale). Results: Age, DAI score, and DRS scores were all correlated with MMAA performance. In a stepwise regression analysis, only DRS scores were predictive of MMAA performance. Among the DRS subscales, conceptualization and memory were the best statistical predictors of MMAA performance. Conclusion: Cognitive functions, especially conceptualization and memory, were the strongest patient-related predictors of his or her ability to manage medications, over and above the effects of age, gender, education level, symptom severity, and attitudes toward medications. These results suggest a need for intervention studies focused on improving, or at least compensating for, specific cognitive deficits such as those in memory and conceptualization among patients with schizophrenia in order to improve their ability to manage medications.