Little is known about the relations between principals' effectiveness in specific leadership tasks and student achievement. The purpose of this study is to explore principal task effectiveness, as perceived by principals themselves and their senior management teams (SMTs), and to explore the associations between perceived principal task effectiveness and student achievement. This study employed an exploratory quantitative design using surveys to collect principal and SMT ratings of principal task effectiveness. In addition, grades from secondary school exit examination in Mathematics and English as a Second Language (ESL) were collected from all public secondary schools in the Maldives. An exploratory factor analysis was used to explore principal task dimensions. Hierarchical regressions were used to examine the predictive ability of principal task effectiveness and certain principal characteristics on student achievement. The analysis revealed five leadership task dimensions: School Management, Instructional Management, Teacher Quality, External Relations, and Program Development and Evaluation. The Teacher Quality dimension positively predicted student achievement in ESL. This research highlights the importance of principal task effectiveness and its link to student achievement. The findings have implications for principals' preparation and professional learning.