Visual pedagogy (VP) is a behavioural intervention used to facilitate learning among autistic children. Limited studies have evaluated VP when applied to dentistry. To evaluate the effectiveness of VP in improving oral hygiene and gingival health status of autistic children. The interventional study was conducted among 122 autistic preschool children and their parents in Hong Kong. Toothbrushing visual pedagogy (TBVP) was provided to parents for supervising their children with toothbrushing at home. The children's sociodemographic background, developmental profile, and clinical parameters were obtained via parental questionnaire, standardised assessment form, and clinical examination, respectively. The change in plaque and gingival indices over time and potential confounding factors were evaluated with Friedman's two-way analysis of variance and logistic regressions, respectively. Significantly lower level of plaque and gingival inflammation was found at 3months and 6months than baseline. The oral health status of children with poorer baseline oral hygiene status and gingival health was more likely to improve with TBVP. Other developmental and socio-economic backgrounds had insignificant associations on the improvement of these clinical parameters. The findings suggest TBVP is effective in promoting oral hygiene maintenance and improving the periodontal conditions among individuals diagnosed with ASD.