This user-friendly revised book on the origin, spread and impact of Islam on Nandi traditional religion and culture from 1850 to 2012, which has not been the subject of scholarly research, attempts to investigate the Islamization in Nandi County; apart from analyzing factors that contributed to the acceptance or rejection of the religion by the Nandi people and consequent challenges of its spread. Cross-cultural and Islamization theories were applied in collecting data and bridging the gap in knowledge. Further, the study utilized both qualitative design and the surveying data collection methods to arrive at the findings. It was revealed that the spread of Islamic religion in Nandi County involved various factors such as socio-cultural, economic, religious and doctrinal, among others. The book is replete with information on proselytism in a cross-cultural context and promotion of inter-faith dialogue, which government-policy-makers, students, researchers and professionals should find both stimulating and useful in addressing the development agenda for Nandi County in areas of education, cultural heritage and religion.