Purpose: This study aimed to define and clarify the concept of medication adherence in the elderly with chronic diseases. Methods: This study employed the hybrid model of Schwartz-Barcott and Kim (2000), which consists of three phases: an initial theoretical phase, a fieldwork phase and a final analytical phase. In the fieldwork stage, data were collected from interviews of 11 elderly people taking prescription medications for one or more chronic diseases in G city. Results: Concept of medication adherence in the elderly with chronic diseases was identified as four dimensions and seven attributes in the final analytical phase: 1) cognitive dimension: mindfulness of taking medication, 2) psychological dimension: expectation of medication, acceptance of taking medication effect, 3) behavioral dimension: spontaneity of taking medication, practice according to prescription or instructions, persistence of taking medication, 4) interpersonal: interaction with healthcare professional. Conclusion: This conceptual analysis improves the understanding of the concept of medication adherence in the elderly with chronic diseases, and could be used as a basis for the development of a measurement tool and nursing intervention of medication adherence in the elderly.