This study aimed to assess the effectiveness of programmes in promoting healthy sexuality, reducing STIs and unplanned teenage pregnancies, and to analyse the moderators of their effectiveness. The results indicated that the interventions were effective in increasing knowledge, promoting attitudes towards sexual health, improving self-efficacy towards condom use, increasing intention to refuse sex, intention to use condoms and condom use. Moderator analyses showed that the interventions were most effective 12-18 months after their application in developed countries (e.g., the United States or Spain), were applied in the school setting, were based on a theoretical basis and did not promote sexual abstinence. It is noted that the effects on nonbehavioral variables (e.g., knowledge or intentions) tend to decrease over time, while the effect on behavioral variables, such as condom use, tends to increase. In conclusion, it is essential to assess the effectiveness of long-term interventions to understand their real impact on young people’s health. To know more about meta-analysis, click here.