OBJECTIVES: To identify studies that delivered an intervention to frail older people to improve medicines optimisation; identify the outcomes reported in these studies; and assess the effectiveness of these interventions on chosen study outcomes. METHOD: Eight electronic databases and four trial registries were systematically searched from the date of inception to April 2020. Inclusion criteria were randomised controlled trials and non-randomised studies of interventions to improve medicines optimisation (including administration, adherence, deprescribing, prescribing and/or medication review) in community-dwelling older people (aged 65 years) with a frailty diagnosis. Only studies published in English were included. A narrative synthesis was conducted, and quality was assessed using an appropriate risk of bias tool. KEY FINDINGS: Searches identified 601 articles; one study met the criteria for inclusion. The single eligible study used a quasi-experimental pre-test-post-test study design to evaluate the impact of a pharmacist-led, team-based medication review for 54 frail older patients living in primary care. Improvements in the total number of medications and prescribing appropriateness were observed. The study was judged to be at an overall serious risk of bias. CONCLUSION: There is a dearth of high-quality evidence demonstrating the effectiveness of medicines optimisation interventions for older people with frailty within primary care. Due to the strong association between patients' level of frailty and adverse outcomes, it is important that future research focuses on proactive interventions which may be beneficial to this patient population.