The purpose of this research is to find out the forms of relations and the factors that influence social relations between Muslim and Christian communities in Nagari Koto Nan Duo. The reason the researcher examines this study more deeply is because the background of the problem in this research is based on the social relations between the Muslim and Christian communities in Nagari Koto Nan Duo, where the social relations between the Muslim and Christian communities in Nagari Koto Nan Duo are indeed reflected in everyday life in a real way. Although geographically there is a separation of residential areas between the Muslim and Christian communities, this does not become a barrier in establishing communication and social cooperation. The research method used is descriptive quantitative research by describing a phenomenon that occurs in society which observes how the relationship between the Muslim and Christian communities takes place. The informants in this study consist of key informants, namely the Muslim and Christian communities, and supporting informants such as the village staff and religious leaders. In collecting data, the researcher used observation, interviews, and documentation techniques. The data analysis method used is data reduction, data presentation, and drawing conclusions. Based on the results of this study, the description of the relations between the Muslim and Christian communities is: (First) The forms of relations between the Muslim and Christian communities consist of cooperation, tolerance, accommodation, competition, conflict, and resolution. (Second) The factors influencing social relations are internal factors, including values and social norms, social status and roles, and religious beliefs. While external factors include economic factors, socio-cultural factors, and ecological factors.