Background: Medication literacy encompasses the cognitive and social skills necessary for individuals to obtain, comprehend, communicate, calculate, and process medication-related information necessary to make informed decisions. Personal and contextual factors are widely recognized to influence the way that individuals acquire and maintain medication literacy skills. Despite a growing number of studies on medication literacy, current definitions remain general, lacking consideration for the specificities of older adults and hospitalization. Objective: The project was conducted to identify, compare, and summarize the attributes, antecedents, and consequences of medication literacy in hospitalized older adults and to propose a refined definition. Methods: A three-phase hybrid model of concept development was performed that included a literature review and focus groups with hospital nurses. In the final analytic phase, findings from the literature and focus groups were compared, and a refined definition of the concept was elaborated. Key Results: From the synthesis of 24 publications and the narrative data of 14 hospital nurses, 19 themes were described: 4 related to attributes, 8 to antecedents, and 7 to consequences. Medication literacy of hospitalized older adults has been further defined as the degree to which older adults and/or their natural caregivers can develop and maintain multidimensional skills, namely functional, interactive, and critical medication literacy skills. Adjustment of these skills is characterized by a dynamic and potentially complex process. In practice, optimal medication literacy might be achieved through control of and involvement in the medication regimen and the decisions related to it, and/or by using practical means to facilitate medication self-management (e.g., using lists, notes, reminders). Conclusions: The proposed refined definition might enhance professionals' common understanding of the concept and its application in practice, policy, and research. Managing a medication regimen is a complex activity that requires a high level of integration and coordination of cognitive and social skills.