This study investigated the Effect of Self-Management Technique on Aggressive Tendency among Secondary School Students in Nnewi North Local Government Area of Anambra State. Three research questions guided the study, while three hypotheses were tested at 0.05 level of significance. Quasi-experimental research design was adopted for this study. The population for this study was a total of 873 junior and senior (JSS2 and SS2) aggressive tendency students from all public secondary schools in Nnewi North. Research sample consisted of 80 students with the highest test scores in the aggressive tendency measuring instrument selected through purposive sampling technique. The Researchers used an instrument called Aggressive Tendency Questionnaire (ATQ) for collection of data for this study. Data collected from this study were analysed using mean and ANCOVA. Results obtained from the study indicated that self-management technique was effective in reducing aggressive tendency among the participants. The results equally showed that self-management technique was more effective in reducing aggressive tendency among the female participants than their male counterparts. Also, the results indicated that self-management technique was more effective in reducing aggressive tendency among the senior students who participated in the experiment than their junior counterpart. Furthermore, the results indicated that there was a significant decrease in aggressive tendency among students in the experimental group when compared with those in the control group. However, the difference in the effects of self-management technique on students’ aggressive tendency was not significant based on gender and age. Based on the findings of this study, some recommendations were made. The researchers recommended, among others, that self-management technique should be adopted by counsellors and other helping professionals as an effective counselling technique in reducing secondary school students’ aggressive tendency. School counsellors should therefore ensure that they acquire adequate knowledge of the technique so as to be able to help students with aggressive tendency effectively.