This study is to analyze the implication of Sex Education in Modern Subjects on the morality of the Muslim Ummah in Kaduna State, Nigeria. The research was motivated as a result of differences of opinion about the introduction of sex education into the curriculum of studies in secondary schools in Kaduna State. In view of this, Survey research design was used in this research and the research used three types of Questionnaires, first to the Islamic Scholars, the second to the Subject Teachers and the third to the Muslim Communities in order to collect their opinions which served as a data for analysis in this research. Simple percentage was used in analyzing the data collected. Consequently, the research revealed the major findings of this research as, teaching sex education will promote moral decadence of the students; instilling consciousness of God is what can mostly promote moral consciousness of the students, Philosophy of sex education does not conform to the cultural practices of the Muslim localities, religious education and guidance is the main way to promote moral values among the members of Muslim localities, and that attempt to pollute the societies is the main idea of introducing sex education. The researcher recommended that the teaching of sex education should be in line with Islam as the western sex education is not in line with the ethical teachings of Islam. Summary, conclusion and recommendations were made.