Background: People with mild intellectual disability (ID) experience a higher prevalence of mental health (MH) problems in comparison to the general population, yet there is little consensus on the most appropriate type and nature of services for support and treatment for this specific group of individuals. Objective: The objective of this scoping review is to explore the current evidence for the organization, structure, and delivery of mental health services for people with mild ID. Methods: The PRISMA-SCr (Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews) checklist was followed. Online databases were used to identify systematic reviews, meta-analyses, scoping reviews, or guidelines published between 2003 and 2020. Articles were reviewed using Roever & Zoccai criteria for critical appraisal of systematic reviews and meta-analyses. Results: 130 records were identified, of which 91 were longlisted. Of these, 28 articles were shortlisted after review of abstracts prior to review of full-text papers. The review included 11 studies: one meta-analysis, eight systematic reviews, and two scoping reviews. These studies approached the provision of mental health services for individuals with mild ID from various angles – including service organization and access, therapies, and patient feedback. Conclusions: According to the Roever & Zoccai criteria, there was a lack of high-quality evidence, which limited the findings and conclusions. The available evidence suggested that despite higher levels of psychopathology there is not a corresponding consideration in care for individuals with mild ID in general psychiatric services. There was no conclusive evidence on better level of services or outcomes being provided either by the general psychiatric services or specialist ID psychiatric services. Some evidence was found for intensive case management and assertive outreach for individuals with mild ID, but this was not replicated in further studies. In terms of treatment, there was no high-quality evidence found for pharmacological interventions, with some limited evidence around psychological therapy for the treatment of depression in this vulnerable population. Overall, it was found that an increase in staff training would be beneficial in terms of timely access to services and appropriate treatment. There is a need for inclusive, evidence-based guidance as regards service development for people with mild ID and MH problems.