Background: People with intellectual disabilities (ID) typically have poorer oral health. Oral diseases have a microbiological origin, and thus, dental plaque control (DPC) is key to safeguard their oral health. Methods: A structured search strategy was applied to screen oral health promotion initiatives for DPC among children and adolescents with ID following PRISMA statements. Qualitative and quantitative analyses were performed. Results: From 1,455 citations, 22 studies informed this review. Seven studies related to mechanical interventions and 13 to chemical interventions. Qualitative analyses found conventional toothbrushes were less effective than modified toothbrushes but quantitative analyses were conflicting. Of the nine studies that compared chlorhexidine to placebos, seven reported chlorhexidine was more effective than placebos. Meta-analysis favoured chlorhexidine to placebos (p < 0.0001, 95% CI 0.34-0.63). Conclusions: Both mechanical and chemical interventions are effective for DPC. It is unclear whether they are alternative means for DPC or whether they are best employed together.