Background: Girls with a mild intellectual disability generally receive less sexuality education than their non-disabled peers, while their needs for sexual knowledge are possibly greater. This study aimed to evaluate the effect and process of a new sexuality education programme (Girls' Talk+), focused on sexual health among girls with a mild intellectual disability in the Netherlands. Methods: A mixed methods approach was applied, using participant questionnaires (n = 249), logs written by trainers (n = 17) and interviews with trainers (n = 10). Descriptive statistics and linear regression models were used to analyse the quantitative data. Several coding phases were used to analyse the interviews. Results and conclusions: This study provides some indication that Girls' Talk+ has positive results on improving knowledge, attitude, and self-efficacy in relation to sexual health as well as trainer and participant satisfaction with the programme.