Multimorbidity is common in older people and makes their care more challenging, for example in terms of adherence to prescribed medicines. Nurses have a pivotal role in supporting patients to adhere to their drug regimen. This article reports the findings of an integrative review of the literature on the influence of personal beliefs on adherence to medicines in older people with multimorbidity. Adherence to medicines was influenced by personal beliefs, such as people’s views on the efficacy of medicines, fear of dependency, concerns about polypharmacy, illness perception, beliefs regarding alternative therapies, religious beliefs, social responsibilities and routines. Integrating biopsychosocial insights into nursing practice and providing person-centred and holistic care to older people with multimorbidity can support their adherence to treatment and therefore improve their health outcomes.