In Portugal, we can see an increasing trend of HIV/AIDS linked to the population over 50 years and the main form of transmission is through unsafe sexual contact. On the other hand, peer education has been one of the privileged methods in changing and reducing sexual risk behaviours, attitudes and beliefs related to HIV/AIDS. Based on these assumptions, the Portuguese League Against AIDS tested the efficacy of a Peer Education Program, targeting adults older than 45 years, carried out over three years. A sample composed of 193 participants was studied, 111 males and 82 females, aged 45–80 years (M = 58; SD = 8,593). A self-report was administered in two different moments, pre and post-intervention, to measure HIV/AIDS-related knowledge, risk perception and sexual risk behaviours. During the intervention, the participants were exposed in a weekly basis to a set of activities which involved information dissemination and a variety of proactive empowerment activities to motivate and involve the target group. The obtained results have shown that, after the intervention programme, participants reported having more HIV/AIDS knowledge, higher risk perception and more condoms use. Comparisons between who reported having done HIV test before and who reported never having done HIV test have shown a significant interaction effect in HIV/AIDS knowledge and risk perception: participants that have never done the HIV test reported more HIV/AIDS knowledge and higher risk perception after the intervention programme, compared to participants who have had the test and to pre-intervention, showing that the programme produced important effects on awareness level and condoms use. Results were discussed according to literature and their relevance to the development and implementation of specific prevention strategies targeting this age group, allowing them to participate in the development process, in spite of the myths about HIV/AIDS and beliefs about the sexuality of the elderly.