The progress of a school is determined by the quality of leadership and the effective performance of teachers. Efforts and breakthroughs to encourage effective teacher performance can be achieved in various ways, including through millennial leadership styles and emotional intelligence. This research aims to measure the influence of Millennial Transformational Leadership and Emotional Intelligence on Teachers' Effectiveness when mediated by Organizational Citizenship Behavior in the XYZ School Foundation in Manado City. A survey was conducted on 53 teachers from the XYZ schools, specifically the elementary and junior high school units, using 25 statement items. Data processing and analysis were carried out using the Structural Equation Modeling-Partial Least Squares (SEM-PLS) method in the Smart-PLS 4 application. The research results indicate that Millennial Transformational Leadership and Emotional Intelligence have a positive impact on Teachers' Effectiveness, with Organizational Citizenship Behavior serving as a mediator. / Kemajuan sekolah ditentukan oleh kualitas kepemimpinan dan kinerja guru yang efektif. Upaya dan terobosan untuk mendorong kinerja guru yang efektif dapat dilakukan dengan berbagai cara termasuk lewat gaya kepemimpinan milenial dan kecerdasan emosional. Penelitian ini bertujuan untuk mengukur pengaruh Millenial Transformational Leadership dan Emotional Intelligence terhadap Teachers Effectiveness dengan mediasi Organizational Citizenship Behavior pada Yayasan persekolahan XYZ Kota Manado. Survei dilakukan terhadap 53 guru yang berasal dari persekolahan XYZ khusus unit SD dan SMP dengan 25 item pernyataan. Pengolahan dan analisis data dilakukan dengan menggunakan metode SEM-PLS pada aplikasi Smart-PLS 4. Hasil penelitian menunjukkan bahwa Millenial Transformational Leadership dan Emotional Intelligence berpengaruh positif terhadap Teachers Effectiveness dengan Organizational Citizenship Behavior sebagai mediator