The purpose of this study is to identify the moderating effect of teacher-student support and conflict relationships between learning motivation and academic engagement of elementary school students. This study used ClassNet data from the fourth year and included 769 students (male 392, female 377) of 39 elementary school classes. Learning motivation and academic engagement were self-reported and teacher-student support and conflict relationships were measured using the peer nomination. The teacher-student relationships are transformed into class-level variables. The significant findings were as follows: First, the analysis result of group differences by gender of the mean of each variables showed that intrinsic motivation was not affected significantly by gender, whereas extrinsic motivation was higher in boys than in girls. Teacher-student support relationship was higher in girls than in boys, and teacher-student conflict relationship was higher in boys than in girls. Second, the multi-level analysis indicated that intrinsic motivation and extrinsic motivation had significant main effect on academic engagement, and teacher-student support in class showed a significant moderating effect between intrinsic motivation and academic engagement. Therefore, as an educational implication, we suggested the importance of teachers’ attitude to foster emotional interest and support for students, in order to increase elementary students’ school engagement.