Purpose: To identify and map the scientific evidence regarding factors associated with the nonadaptation of completely edentulous patients to mandibular complete dentures. Materials and Methods: This scoping review followed the PRISMA-ScR statement for Scoping Reviews and was based on guidelines proposed by Arksey and O'Malley and the Joanna Briggs Institute Manual for Evidence Synthesis. The methodology was registered on the Open Science Framework. An electronic search strategy was conducted in PubMed/MEDLINE, Web of Science, Scopus, Cochrane Library, Virtual Health Library, ClinicalTrials.gov, Google Scholar, and ProQuest databases was conducted. Studies that evaluated factors associated with adaptation to and acceptance of mandibular complete dentures were included, such as sociodemographic, psychologic, patient-related, and denture-related items. Results: The search conducted in March 2022 yielded 9,978 studies. In total, 24 studies were included for data extraction. Sociodemographic factors did not interfere with adaptation to a mandibular complete denture. Psychologic factors and patient-related aspects showed greater association with nonadaptation to mandibular complete dentures than denture-reported factors. Conclusion: Although it is suggestive that psychologic and patient-related factors have higher association with the acceptance of new dentures, data must be interpreted with caution due to the variability of methodologies of the studies included in this review.