Besides families, schools represent the second social environment where children and adolescents spend a lot of their time, and on which a large part of their learning and development depends. The purpose of this study is to access the awareness and perception of adolescents on the effectiveness of school-based mental health interventions. The research design adopted for this study was a descriptive cross-sectional study. The research was carried out in Queens School, Rivers state. The target population for this study was focused on adolescents attending Queens
School which comprised of 200 adolescents. A sample size of 80 respondents was gotten using Nwanas' formula. Sampling technique adopted was a simple random sampling technique. A criterion mean of 2.5 was used to compare the results. The results from the study showed that there was high level of awareness of adolescents on the effectiveness of school-based mental health interventions with an overall grand mean of 2.9, higher than the criterion mean. In the same way, there was an overall high perception of adolescents on the effectiveness of school-based mental health intervention with an overall grand mean of 3.02, higher than the criterion mean. Lastly, there was high effectiveness of counsellors on school-based mental health interventions with an overall grand mean of 2.07 which are all higher than the criterion mean. The study proved that the majority of adolescents were all aware about mental health but some did not practice seeking help. Therefore, mental health programs such as counseling, therapy and support groups, should be made available in the school, counselors should also be accessible and have a welcoming attitude towards students. A follow up should be done to ensure their adolescents are free from any long term effects in the future