Aggression among secondary school students remains a significant psychological and educational challenge in Nigeria, undermining school safety, students' academic achievement, and psychosocial well-being despite the disciplinary measures implemented by school authorities. Accordingly, this study investigated the effectiveness of Cognitive Restructuring (CR) and Reality Therapy (RT) as psychotherapeutic interventions for reducing aggression among secondary school students in Ogun State, Nigeria. A quasi-experimental pre-test–post-test control group design was employed, involving 211 participants selected through a multistage sampling procedure from three public secondary schools. The data collected through Student Aggressiveness Scale (SAS) were analysed using Analysis of Covariance (ANCOVA), and an independent t-test, respectively. The findings revealed a statistically significant difference in post-test aggression scores among the groups. Students who received Cognitive Restructuring or Reality Therapy demonstrated significantly lower aggression levels than those in the control group. The study concludes that Cognitive Restructuring and Reality Therapy are effective psychotherapeutic interventions for reducing aggression among adolescents. The study recommends integrating structured psychological interventions into secondary school counselling services to reduce aggressive behaviour and promote students' psychosocial well-being.