Consanguineous marriage is traditionally common throughout the eastern Mediterranean region. Research has suggested that it is closely linked to the sociocultural and socioeconomical status of individuals, and education plays a critical role in decreasing the number of cases. This study aimed to determine the effects of a formal training programme on consanguineous marriages on the knowledge of, and attitudes towards, consanguineous marriage of high school students (n=804) in the Mediterranean region of Turkey. Seniors from three randomly selected public high schools participated in the pre-test and post-test design study. To determine the effects of the programme, students who received the training were compared with those who did not receive any formal training about the subject. After the post-tests were administered, data were collected and analysed using chi-squared and McNemar tests. The results showed significant differences in knowledge and attitudes among the students who had received the formal training programme and those who had not. In addition, the results indicated potential peer influence between the students who received training in consanguineous marriage and those who did not.