The lack of optimization of the principal's managerial competence in managing the Full Day School program is still a significant problem in improving the quality of education in Islamic boarding schools. This study aims to identify the managerial competence of the principal of the Tahfizul Qur'an Darussomad Islamic Boarding School in managing and developing the Full Day School program. This study uses a qualitative approach with a case study type. Data were collected through interviews and documentation, then analyzed using data reduction, presentation, and verification techniques. The results of the study indicate that: (1) the ability to prepare school plans systematically but needs to improve coordination of implementation; (2) human resource management is quite good but the distribution of tasks and training is still not optimal; (3) transparent management of student affairs and new student admissions but is constrained by facility capacity; and (4) curriculum management that is relevant to national education goals but faces limited implementation time. Improved coordination, teacher training, and facility adjustments are needed to optimize the principal's managerial competence in implementing the Full Day School program in Islamic boarding schools. Thus, this study argues that strengthening the principal's managerial competence is a strategic need to ensure the effectiveness of the implementation of the Full Day School program in order to improve the quality of education in Islamic boarding schools.