ABSTRACT This study aimed to assess the effectiveness of a sexual development education programme designed for the mothers of primary school pupils in Türkiye. The programme’s impact on participants’ perceptions of sex education was evaluated using a 2 × 2 experimental design. Thirty participants, all mothers of primary school students, were assigned to either the experimental or control group. Data collection tools included a Personal Information Form, an Opinion Questionnaire on Sex Education, and the Sex Education Programme Knowledge Test (SEPKT). The experimental group participated in an 8-week Sexual Development Education Programme. Pre-test analysis revealed no significant differences between the experimental and control groups; however, post-test analysis indicated a significant improvement in SEPKT scores for the experimental group compared to the control group. Post-test results also showed that participating mothers held more positive views about sexual development education compared to their pre-programme perspectives. This research contributes to understanding the impact of targeted interventions in sex and sexuality education. The findings underscore the importance of providing comprehensive sex education programmes with targeted interventions for parents in Türkiye, which can positively influence their ability to communicate and provide appropriate education to their children.