This research aims to explore the causes and efforts in building a peaceful classroom climate. This research was conducted at Bandung City Elementary School X. The method used in this research is a single case type study (single instrumental case study). The data used in this study are based on interviews, observations and documentation. Participants in this study consisted of 5 teachers and 6 students. Determination of student participants based on observations confirmed by the homeroom teacher, students who were made participants were 4 male students and 2 female students consisting of 2 students behaving disturbingly, 2 students disinterested, and 2 students who obeyed. The results of the study stated that the behavior of one student could influence the classroom climate. The 4th grade climate felt peaceful when one student was absent. This raises a variety of other problems that cause the climate seems not peaceful, among others, disruptive behavior of students, noisy class, and breaking the rules. As for building a peaceful class climate, it can be done by setting clear rules. The rules are arranged based on the agreement of students and teachers giving rewards and punishment, are consistent and strict in applying the rules made, and fostering the character of mutual respect between class members. A peaceful classroom climate is built together, school residents can remind each other in the process of its application.