There is a major political commitment at the European Union level to providing good quality sexuality education in schools. Multiple studies in the World Health Organization (WHO) European Region have demonstrated the importance of sexuality education for the health and well-being of children and adolescents. Parents' role in providing information about sex, sexuality and relationships has also been widely recognised, though we know little about the involvement of parents in school-based sexuality education and the possible outcomes. We conducted a scoping review to systematically identify initiatives within the WHO European Region that involve parents in school-based sexuality education. We identified five programmes -- four of which had been implemented in the UK and one in Turkey. In addition, online expert consultations provided professional insights and resources related to the topic. This review indicates that initiatives to involve parents in school-based SE exist within the region. Although our results refer to the benefits of involving parents in school-based sexuality education, such as improving communication between parents and children and contributing to parental trust in a school's approach to sexuality education, it also indicates barriers, for example, lack of time on the part of parents and teachers.