Teachers are key guidance figures in the lives of high-ability students. By building and maintaining close relationships with their students, teachers may heavily affect the socioemotional development of high-ability students. This study investigated how the teacher-student relationship quality affected the development of high-ability students' academic engagement. Additionally, we examined if the teacher-student relationship quality was more important for the engagement of at-risk high-ability students (i.e. students with a low SES background or students with a diagnosed learning disability or developmental disorder). A sample of 403 Flemish high-ability students (IQ [greater than or equal to] 120) reported on their behavioral and emotional (dis)engagement using scales developed by Skinner and colleagues (2009) and their relationship with their teachers using the People in My Life questionnaire (Cook et al. 1995). Multilevel growth curve analyses showed that positive and negative teacher-student relationships both contributed to the development of high-ability students' behavioral and emotional (dis)engagement. Analyses also revealed that negative relationships had a stronger effect on the behavioral disengagement of low SES students. The emotional (dis)engagement of students with a diagnosed learning disability or developmental disorder was less affected by a negative teacher-student relationship. Results highlight the key position of the teacher in creating an engaging environment for high-ability students.