Autism Spectrum Disorders (ASDs) are neurodevelopmental disorders that don’t have a direct effect on oral health, but severe difficulties in oral hygiene and dental procedures expose people with ASDs to an increased risk of oral diseases. This RCT aimed to evaluate which pedagogical tool was the best to prepare children with ASDs for their first dental examination, either video or photo aids. Two different criteria were used to evaluate their efficacy: the achieved steps into which the procedure was divided (n = 8), and the level of cooperation according to the Frankl Behavioral Scale. One hundred-thirteen subjects were randomly assigned to the two groups and 84 subjects completed the trial (Video group n = 41; Photo group n = 43). A predictive model for the achievement of the Preliminary (1–4) or Dental (4–8) steps was performed using a multivariate logistic regression procedure. Children in the Video group achieved more steps, but the comparison between groups was statistically significant only for the Preliminary steps (p = 0.04). The percentage of subjects judged as cooperating was similar in the two groups. The results of this study underline that behavioural intervention should be used as an effective strategy to prepare subjects with ASDs for a dental examination.