As the Mediterranean diet (MDi) has demonstrated a powerful preventative effect on various medical conditions, a positive effect on oral health may also be speculated. Tooth loss, pain or tooth mobility may discourage the consumption of specific food types, affecting MDi adherence. The aim of this study was to investigate the association between adherence to MDi and oral health in adult populations. The study protocol was registered in Open Science Framework (https://osf.io/vxbnh/) and adhered to PRISMA-ScR guidelines. The principal research questions were: (1) Does better oral health enable adults to better adhere to MDi? and (2) Does better adherence to MDi enable adult individuals to have better oral health? The content of three databases, Clarivate Analytics’ Web of Science, Scopus and PubMed was searched without language, date or any other restrictions. The search results were imported into the Rayyan environment, and from the initial 1127 studies identified, only 20 remained after the exclusion process. Three articles composed the first group, revealing significant associations between various oral health parameters and adherence to MDi, with large variations in methodology and no safe conclusions. The studies investigating the effect of the level of adherence to MDi on various oral parameters were more numerous and revealed negative associations with the prevalence of periodontal disease and upper aero-digestive tract cancer. Further studies to explore the existence and direction of the association between oral health and MDi are needed, with public health interventions encouraging adherence to the MDi to reduce the burden of oral conditions and other non-communicable diseases.