Background: Students with intellectual disability often do not receive holistic sex education, which is critical for their successful transition to post-school life, including having an ability to make healthy choices about their sexuality and relationships. The aim of this inclusive research study was to explore the perceptions and experiences of sex education with Australian high school girls with intellectual disability, as they prepare for a transition to post-school life. Method: There were 11 high school girls aged 13-20 years who participated in this study. Interviews were conducted and analysed using inductive content analysis. Findings: The findings indicate that critical topics such as gender and sexual identity, and masturbation are not sufficiently covered in sex education in New South Wales, Australia. The participating girls also highlighted ways in which teachers could make sex education lessons more accessible. Individual Learning Plan meetings, an important platform for transition planning, were attended by less than a third of the girls in this study. Conclusions: Comprehensive and accessible programmes on sex education for high school girls with intellectual disability are needed to promote successful transition to an autonomous life for these students.