Abstract This study examines the influence of transformational leadership on teacher effectiveness in secondary schools. In contemporary educational systems, leadership plays a critical role in shaping instructional quality and student outcomes. Transformational leadership, characterized by idealized influence, inspirational motivation, intellectual stimulation, and individualized consideration, has been widely associated with improved organizational performance. This paper explores how these leadership dimensions affect teacher effectiveness, defined as instructional competence, classroom management, student engagement, and professional commitment. Using a descriptive survey design supported by an extensive literature review, the study establishes that transformational leadership significantly enhances teacher effectiveness by fostering motivation, collaboration, and professional development. The findings underscore the need for leadership training programs and policy reforms that prioritize transformational leadership practices in secondary school administration.