Abstract Sex education in schools can play an important role in improving young people’s sexual health. Dutch youth are often dissatisfied with the sex education they receive at school; they want more attention to discussing pleasure, consent and diversity. While there have been various calls for positive and inclusive sex education over the past decade, still very few schools provide it. This study examined teachers’ perspectives on positive and inclusive sex education and documents the barriers teachers are confronted with in providing this type of sex education. Based on an online questionnaire survey of 508 sex education teachers, we examined the extent to which teachers possess the knowledge, attitudes and skills that facilitate the delivery of positive and inclusive sex education. We also held focus groups with 25 teachers from 10 schools and explored what they consider to be key barriers and best practices in teaching positive and inclusive sex education. Teachers overall have the knowledge, attitudes and skills that are needed to provide positive and inclusive sex education, but there is room for improvement, for example regarding knowledge on intersex individuals and the clitoris. Teachers experienced barriers at three levels: the personal level (e.g. personal discomfort), the classroom level (e.g., safety in the classroom) and the structural level (e.g. sex education not being part of the national curriculum; lack of time). Structural barriers seem to be at the basis of the barriers at the personal and classroom level. It is advised that positive and inclusive sex education gets a permanent place in the national curriculum. By developing concrete core objectives in the area of relationships, sexuality and diversity, for all grades, and by providing more extensive teacher training, teachers and schools will be facilitated to organize sex education in a more sustainable way. Key messages • Sex education teachers in the Netherlands desire better training to provide positive and inclusive sex education in the classroom. • Integrating sex education in the national curriculum would help teachers to address sexuality in a more sustainable way in the classroom.