Background: Bariatric surgery results in substantial medical and economic benefits; however, independent studies typically report high patient preoperative attrition rates. Studies have identified individual characteristics and sociodemographic variables of those who complete the surgery compared to those who do not. The aim of the present protocol is to outline a systematic review focussed on identifying the sociodemographic, medical, cultural, psychological, and patient-led factors affecting preoperative attrition in clients who were enrolled in bariatric surgery programmes. Methods/design: The databases Scopus, CINAHL, PsycINFO, Web of Science, and MEDLINE will be searched for retrospective, prospective, and cross-sectional observational studies that have identified any sociodemographic, medical, cultural, psychological, and patient-led factors affecting preoperative attrition in clients who are enrolled in a bariatric surgery programme. English-language articles published between 1997 to 2020, inclusive of adults 18 years or older, will be included in the review. This protocol has been registered in PROSPERO, registration number; CRD42017068557. Discussion: Presently, there are studies and reviews investigating population-based utilisation and access to bariatric surgery; however, there is a need to review the reasons behind preoperative bariatric surgery patient attrition once selected for bariatric surgery. The results of the review will highlight potential systematic disparities in patient attrition, where gaps in knowledge remain for further investigation, and suggest areas where countermeasures may be focussed for decreasing attrition rates.