Bullying is a social phenomenon that has become a complex problem worldwide due to the complications that arise from its persistence among school-going adolescents. This study explored the causes of bullying among grades 8 and 9 in one secondary school in Amatole East District, Eastern Cape Province, South Africa. This qualitative study employed constructivist paradigm and a case study design. It utilised interviews to elicit data from 15 purposefully sampled participants. This study was informed by Travis Hirschi's 1968 Social Control Theory, and I used Braun and Clark's thematic analysis steps to analyse and interpret the data. The study found that bullying is triggered by jealousy and envy among learners, inadequate school furniture, family environment, physical attributes, lack of moral education, lack of sexual orientation education, and age differences among learners. Therefore, the study concluded that in order to detect the causes of bullying among grade 8 and 9 learners, teachers must apply Social Control Theory in the school environment by establishing consistent and supportive teacher-learner relationships to easily identify learners' behavioural changes and promote support, peer relationships, and unity among learners. This will reduce internal motivation that leads them to initiate bullying and violate other learners' rights. Additionally, the findings of this study will enable school stakeholders to develop intervention strategies, including disciplinary measures for learners, providing sexual orientation education, and involving parents in their efforts to manage bullying among grades 8 and 9 learners.