BackgroundPolypharmacy (≥5 medications) is common in older patients and is associated with adverse outcomes. Patients’ beliefs about medication can influence their expectations for medication, adherence, and willingness to deprescribe. Few studies have examined beliefs about prescribed medication among older patients with polypharmacy in primary care.AimTo explore medication-related beliefs in older patients with polypharmacy and factors that might influence beliefs.Design and settingA mixed methods study utilising data from a randomised controlled trial aiming to decrease potentially inappropriate prescribing in older patients (≥70 years) in Ireland.MethodBeliefs were assessed quantitatively and qualitatively. Participants completed the Beliefs about Medicines Questionnaire by indicating their degree of agreement with individual statements about medicines on a 5-point Likert scale. Semi-structured qualitative interviews were conducted with a purposive sample of participants. Interviews were transcribed verbatim and a thematic analysis conducted. Quantitative and qualitative data were analysed separately and triangulated during the interpretation stage.ResultsIn total, 196 patients were included (mean age 76.7 years, SD 4.9, 54% male), with a mean of 9.5 (SD 4.1) medications per patient. The majority (96.3%) believed strongly in the necessity of their medication, while 33.9% reported strong concerns. Qualitative data confirmed these coexisting positive and negative attitudes to medications and suggested the importance of patients’ trust in GPs in establishing positive beliefs and potential willingness to deprescribe.ConclusionParticipants reported strong beliefs in medications with coexisting positive and negative attitudes. The doctor–patient relationship may have influenced beliefs and attitudes towards medicines, highlighting the importance of strong doctor–patient relationships, which need to be considered in the context of deprescribing.