Abstract Background Medication knowledge, as defined by six aspects, is the person's awareness of their medication name, dose, purpose, adverse drug reaction (ADR), administration schedule and special instructions, is essential in the older patient's treatment journey. This review aimed to assess medication knowledge in older adults. Methods A systematic search of six electronic databases, grey literature and citation indexes included studies conducted in any setting or any country on those 65 or older, published over the last ten years, reporting primary data with full-text access, and assessing patients' six aspects of medication knowledge. Joanna Briggs Institute Critical appraisal tool was used to evaluate quality of studies. Results Of the 67871 articles searched, only 10 cross-sectional studies were included. Medication knowledge data was collected from pharmacies, community, general practices and outpatient clinics. Surveys used face-to-face interviews and electronic, written, and mail questionnaires. Five studies assessed knowledge on single medications. None assessed all six aspects of medication knowledge. One study assessed five aspects, while the rest assessed fewer aspects. The percentage of those who knew their medication names ranged from 41.9% to 97%, dose 19.4%, purpose 15% to 90%, administration schedule 65% to 92.6%, ADR 42% to 80% and special instructions 32.4% to 94.8%. Data lacked the source of medication knowledge or evidence of a patient-centred care approach. There were repeated calls for further education and research. Conclusion Research indicates that older adults have a mixed knowledge of their medications, with some areas well grasped and others lacking. Additionally, it appears that medication knowledge is not thoroughly evaluated initially. Despite ongoing advice to employ all six aspects of medication knowledge for assessment and education enhancement, no progress is seen in older adults' medication knowledge. Therefore, there's a need for better research that anticipates the application of these six aspects, concentrating on education for older adults or their caregivers through patient-centred methods.