Introduction: Pessary use is the preferred non-surgical treatment option for female pelvic organ prolapse. As pessaries can be used chronically to alter pelvic floor anatomy, consideration of shortand long-term complications is important in patient management. We systematically reviewed articles describing the complications of pessary use to determine frequency and severity. Methods: A systematic search via MEDLINE and PubMed using the key terms "complications," "pessary," "pelvic organ prolapse," "side effects" was conducted for the years 1952 to 2014 inclusively. Selected articles cited in the publications identified were also considered. Only full-text material published in English was reviewed. All pessary-related complications described were collated; overall frequency within case reports and case series were calculated and severity was graded using the Clavien-Dindo classification. Results: In total, 61 articles met the inclusion criteria. The most common complications reported were vaginal discharge/vaginitis, erosion, and bleeding. Complications were related to pessary shape and material, and duration in situ. Clavien-Dindo classification of complication severity found that all 5 grade levels were attributed to pessary use; serious grade 4 and 5 complications included cancer, adjacent organ fistula and death. Conclusion: There are few detailed reports of complications of pessary use relative to the estimated frequency of pessary use worldwide. Prospective studies documenting complications by shape, material, and size, and objectively classifying complication severity are required. As serious grade 4 and 5 complications of pessary use occur, further development of clinical follow-up guidelines for long-term pessary users is justified.