Objective To assess the association of metformin prescription with the risk of aortic aneurysm, aortic aneurysm events and the enlargement of abdominal aortic aneurysm (AAA). Design Systematic review and meta-analysis. Methods We searched PubMed, Embase and Scopus for epidemiological studies up to November 2018. We included observational studies which evaluated the association of metformin prescription with the risk of aortic aneurysm disease, and we also included studies involving progression and enlargement of AAA. The Newcastle-Ottawa Scale was used to assess the quality of included studies. Random-effect meta-analyses were conducted in line with the between-study heterogeneity. Sensitivity analyses were performed to identify the source of heterogeneity. Results Eight studies enrolling 29 587 participants met the inclusion criteria and were included in this systematic review. We found that metformin prescription could significantly limit the enlargement of aortic aneurysm (weighted mean difference: -0.83 mm/year, 95% CI -1.38 to -0.28, I-2=89.6%) among patients with AAA. Metformin prescription status may be associated with a decreased risk of aortic aneurysm and aortic aneurysm events. Conclusions According to the available epidemiological evidence, metformin prescription could limit the expansion of AAA among patients with this disease, and may be involved with a lower incidence of aortic aneurysm and aortic aneurysm events. Randomised controlled trials are needed to confirm whether metformin could reduce the enlargement of AAA in patients with or without diabetes.