Young children's temperament was examined as a potential predictor of early adolescent school engagement, with elementary school teacher-child and peer relationships included as potential mediators of these effects. A large national longitudinal dataset (N = 1,032) was used to estimate structural equations models that showed children's social dissatisfaction and teacher-child closeness mediated links from early temperament (i.e., negative affect, effortful control at age 54 months) to early adolescent (age 11) emotional engagement in school. These findings suggest that aspects of teacher and peer relationships in elementary school classrooms are key mediators of the long-term effects of early childhood temperament on later school engagement.