The purpose of this study was to establish effects of Western Christianity and African Traditional Religion on moral and cultural development of the people of Trans Nzoia County. Morals and core values play a very important role in the upbringing of the youth in any given community in any given Geographical part on this planet. The study will be guided by the following objectives: Establish effects of Christianity on moral development, Determine effects of African Traditional Religion on moral development, Compare and contrast effects of moral development of Western Christianity and African Traditional Religion and to determine the role played by morals and core values in both Christianity and African Traditional Religion. Mixed Research method combined both qualitative and quantitative was employed in the study to unearth the hidden truth underlying in the study. The target population was 500 people which gave a sample size of 50Bishops and Pastors of 50 Churches. The researcher employed purposive and simple random sampling techniques. The researcher used two guiding theories in the study: the theory of Atonement on the Christian part and the theory of dual allegiance on the part of African Traditional Religion. Data was collected by use of Questionnaires and Interview schedules. The raw data was analyzed and descriptively availed for facilitation of research objectives and research questions. Computer program SPSS was employed to give the final accurate and precise results of Research findings. The findings indicate that the intrusion of foreign cultures in Trans Nzoia County has helped water down the quality of African morals on one part and the other part there is improvement on cultural and core values of the people of Trans Nzoia County. The conclusion on the same is that since communication and mobility has been so much developed in these resent times, it is easy for people from different parts of the world to meet and interact at any time at any given Geographical zone on the planet. The study recommends that the citizens of Trans Nzoia should be careful enough in considering the kind of morals to be applied in this county since the county is an Agricultural hub where people from different parts of the Earth converge either for commercial purposes or for learning Agri-business techniques.