The aim of this research is to study the impact of teacher leadership on the school effectiveness. A total of 181 teachers from six primary schools in Male (the capital island of Maldives) were chosen as respondents for this study. A quantitative survey method using questionnaire to obtain the data is employed. The findings showed there is a significant relationship between each dimension of teacher leadership and school effectiveness. Multiple regression analysis showed that among the seven dimensions of teacher leadership, autonomy dimension contributes 47.1% to school effectiveness and become the most significant predictor. However, the other two dimensions include positive environment dimension which contribute 6.5% while open communication dimension contribute 2.9% to school effectiveness. The overall findings indicated that there is 56.5% impact of teacher leadership on school effectiveness. This study indicates the importance of studying teacher leadership on school effectiveness as the information collected would help teachers, principals and the education ministry to plan, implement, access and maintain high level of teacher leadership which in turn to promote higher level of school effectiveness. (Contains 6 tables and 1 figure.)