This quasi-experimental study aimed to determine whether a sexuality education intervention, developed through a university–school–health–community collaboration, effectively improved students’ knowledge, attitudes and behaviours regarding sexual health. Utilising project-based and service-based learning, the programme engaged 454 students aged between 13 and 48 years (M = 19.33, SD = 6.03). The quasi-experimental group comprised students from secondary school, a nursing degree and a master’s in teaching, while the control group included students from secondary school and bachelors’ and masters’ degree students in health and education. The intervention was evaluated through pre- and post-surveys incorporating seven standardised measures to assess key areas, including social media use, body image, sexual behaviour, gender attitudes and pornography consumption. Before the intervention, the secondary school students and the students from the bachelors’ and master’s programme in teaching exhibited fewer positive attitudes and behaviours towards sexuality compared to the nursing students. However, following the intervention, the study showed that the university–school–health–community partnership enhanced sexuality education. It fostered trans-inclusive behaviours, promoted positive attitudes towards sexual diversity and reduced sexist beliefs and rape-supportive attitudes. These results highlight the intervention’s effectiveness among the participants.