This systematic review aimed to summarize the current evidence on the effectiveness of various psychological behavioural therapies in improving oral hygiene maintenance habits and oral health among children with autism. Independent screening and study selection, data extraction, risk of bias assessment, and evaluation of the certainty of evidence were conducted. A total of 16 studies were deemed eligible for qualitative synthesis, with 9 included in quantitative analyses. Psychological behavioural therapies including visual pedagogies, social stories, components of PECS (Picture Exchange Communication System) and Applied Behavioural Analysis, as well as the use of smart device applications all demonstrated improvement in oral health parameters following implementation. However, most studies lacked control groups and exhibited a high risk of bias due to the lack of reporting or failure to account for autism spectrum disorder (ASD) severity and associated comorbidities. In addition, studies typically relied on caregivers to carry out reinforcement of therapies, which may explain the significant heterogeneity observed. In summary, the evidence supporting the use of psychoeducational techniques to improve the oral health parameters of autistic children is limited and of very low certainty. Further research utilizing larger-scale studies and more rigorous study designs is necessary to enhance the certainty of evidence in this field.