Background: The affective expression of sexual behaviour in individuals with Williams syndrome can lead to risky behaviours, especially if parents do not have information on how to provide sex education or support from specialised professionals. Method: The Attitudes to Sexuality Questionnaire for Individuals with Intellectual Disabilities was used to identify parental beliefs, attitudes and concerns about the sexuality and sex education of individuals with intellectual disabilities. The sample comprised 35 parents of individuals with Williams syndrome (mean age 12.8 years (SD = 4.5), 57.1% male). Results: Parents believe in the possibility of marriage and sexual relationships for individuals with intellectual disability when they are older and agree with sexual reproduction in adulthood. Parents consider that sex education, in addition to parental guidance, should be provided by professionals. Conclusions: This data highlights the need for parents to have clear guidelines on interventions in respect of the sexuality of individuals with intellectual disability.