Approximately 50% of patients across all age groups with varied types of medical conditions do not adhere to their prescribed medication regimens. Medication nonadherence is common in older adults who are often prescribed medications for age-related chronic disorders. The purpose of this paper is to investigate the effect of personal and cultural beliefs on older adults' medication adherence through a review of research studies published in journals across different disciplines. A systematic literature search using ten databases found 14 articles meeting the inclusion criteria. Belief-laden variables including self-efficacy (i.e. the belief that one can perform a specific behaviour under differing conditions), medication efficacy, confidence in the physician's knowledge, perceptions about natural products and home remedies, beliefs of control (over one's health), and illness perceptions were found to be significantly related to medication adherence among older adults. However, several measurement, design and sampling problems were identified in this review. The majority of the studies in the review evaluated older adults' medication adherence by self-report and used cross-sectional designs and convenience samples. Future studies should utilise prospective longitudinal designs and a more objective measure of medication adherence, such as electronic event monitoring, when examining factors related to older adults' medication adherence. Future research should also evaluate belief-related variables in larger and more ethnically diverse samples of older adults. Implications for assessment and intervention are evident from this literature review of the effect of personal and cultural beliefs on medication adherence in older adults.