Abstract Background School-based comprehensive sexuality education (CSE) is the best approach to disseminate scientific evidence and promote healthier sexual behaviours among young people. However, in Italy, CSE is not included in schools curricula. This study, funded by the Ministry of Health, seeks to investigate information uptake and attitudes towards sexuality among adolescents included in a pilot CSE intervention in 6 Italian regions, from December 2023 to June 2024. Methods A 10-hours education intervention was implemented in a convenient sample of 26 upper and lower secondary schools (U/LSS), covering topics such as changes in adolescence, relationships and consent, sexual identity, sexually transmitted infections (STIs), contraception and sexual health services. Students’ evaluation comprised pre/post tests assessing knowledge, attitudes towards sexuality and satisfaction. A Solomon 4-group design study was used to compare intervention and control classes. A follow-up test will be conducted 4-6 months post-intervention. Results Preliminary analysis of available data as of 30 April, 510 pre-tests and 266 post-tests, showed incremented correct answers in all items. A significant increase (p<.05) was found in 12/21 items for USS and in 9/19 items for LSS, especially in the domain STIs symptoms and prevention, among those mostly appreciated. Over 90% of students considered schools as suitable setting to receive CSE, preferably by external experts. Ongoing qualitative and long-term analysis will provide further insights of the overall impact of the activity. Conclusions The pilot CSE intervention increased the knowledge and attitudes of the students involved. Additional insights will be available after study completion. Findings from this study will contribute to evaluate the effects of CSE initiatives on sexual health knowledge and attitudes among Italian secondary schools students, as well as the effectiveness of such programs in fostering healthier behaviours. Key messages • Providing evidence-based, relevant information and education on sexual health to young people in secondary schools increases their knowledge and improves attitudes towards sexuality. • CSE should be included in Italian school curricula in order to promote an incremental uptake of information and to improve young people’s sexual health.