Background: cousin marriage is a global health issue with a number of negative health and social effects. Aim: To evaluate the effect of educational package about Genetic and Reproductive Consequences of Cousin Marriage on Nursing Students' Knowledge and Attitude. Subjects and Methods: Research design: A quasi-experimental design was used to achieve the aim of this study. Setting: The study was conducted in the Faculty of Nursing, Zagazig University, Subjects: 221 undergraduate nursing students at the 1st semester of academic year (2022/ 2023). Tools of data collection: Three data collection tools were used: A Structured interviewing questionnaire sheet, knowledge assessment sheet, and a Likert scale for assessment of students' attitude. Results: The study indicated that more than two thirds of the studied students had total correct knowledge and more than four fifth had a positive attitude regarding consanguineous marriage post-intervention. Conclusions: A significant improvement of student's knowledge and attitude related to cousin marriage and genetic disorders influence offspring after educational sessions was revealed. Recommendations: Based on this finding, the study suggested incorporating premarital counselling ideas related to consanguineous marriage into curricula at undergraduate universities. Keywords: Consanguineous marriage, premarital counseling, attitude, nursing students