Objectives The use of an anatomical side marker (ASM) on x-rays, be it digital or radiopaque, is an important quality and safety concept within general radiology. Using radiopaque ASMs is best practice, and lack of any ASMs may have dire consequences in terms of patient safety. To date, there have been no systematic reviews investigating the use of ASMs in clinical practice. Methods A systematic search of electronic databases (CINAHL, the Cochrane Library, Medline, EMBASE, ERIC, and JBI) from inception to March 1, 2018, was undertaken. Gray literature searching (through Google) and pearling was conducted. Methodological quality was assessed using a modified version of the McMaster Critical Appraisal tool for quantitative studies. A customized data extraction tool was developed, which included characteristics of the studies. Results Of 624 studies, 7 studies met the eligibility criteria. Despite diverse study designs, collectively, the studies demonstrated that only a small number of x-rays did not include an ASM. On x-rays that did use a radiopaque ASM, most of them were positioned in the primary radiation field. A noticeable shift in practice from the use of radiopaque ASMs to digital ASM was also identified. Multifaceted barriers were reported for the use of ASM in routine clinical practice. Conclusions Although missing ASMs on x-rays were a small feature, findings from this review highlight opportunities for improvement and a need to ameliorate barriers for ASM use.