Purpose: Medication adherence in older adults with multimorbidity is critical for self-care. The purpose of this cross-sectional study was to identify the factors that influence medication adherence in older adults with multimorbidity. Methods: The patients were 116 adults 65 or older with three or more chronic diseases. The data were collected from December 2020 to April 2022 in outpatient clinics at a hospital in Daejeon. Results: The mean scores of depression, social support, and medication adherence were 16.18±6.74 (of 30), 41.06±6.56 (of 60), and 4.69±1.85 (of 8) points, respectively. Patients with low adherence comprised the most with 75 patients (64.7%). Influencing factors on medication adherence were depression (β=-.35, p=.007) and family support among social support (β=.29, p=.006). Conclusion: Among older adults with multimorbidity, lower depression as well as higher family support, results in higher medication adherence. It is necessary to develop a practical strategy toward improving medication adherence, by sensitively managing the degree of depression, as well as strengthening family support.