This study explored the psycho-social dynamics by examining the effect of assertiveness technique on low academic self-concept among secondary school students in the Onitsha education zone. Two research questions guided the study, and two null hypotheses were tested at a 0.05 level of significance. The study design was quasi-experimental, non-randomised pre-test and post-test, control group research. The population of the study was composed of 988 senior secondary school students in the Onitsha education zone, and a sample of 70 students was selected through purposive sampling. The data was collected using the Academic Self-Concept Survey (ASS) questionnaire, and the internal consistency reliability coefficient of the instrument was 0.84. The questionnaires were administered through direct delivery. Mean scores were used to answer the research questions, and the null hypotheses were tested using Analysis of Co-variance (ANCOVA). The instrument norm of 72.50 was used to make decisions when answering the research questions. The findings of the study showed that assertiveness training was effective in improving the low academic self-concepts of secondary school students. Furthermore, it was revealed that the assertiveness training technique was more effective in improving the academic self-concepts of female secondary school students. Based on the findings and implications of the study, it was suggested that counsellors and therapists should use modelling and assertiveness training techniques in counselling sessions to enhance the academic self-concepts of secondary school students.