Purpose: To fill the gap in theoretical and empirical knowledge on the patterns of organizational citizenship behavior (OCB) in school, the aim of this study was to explore the components of teacher OCB as well as its personal and contextual determinants. Research Design: Semistructured interviews were conducted with 50 schoolteachers, 10 principals, and 10 supervisors, all from the elementary and secondary educational systems of Israel. The analysis followed the principles of qualitative research. Findings: The article presents an initial conceptualization of the components of teacher OCB. Among these components are supportive behaviors toward students and colleagues, initiation of changes and innovations in teaching, strong orientation toward the organization, and strong loyalty to the teaching profession. In addition, the study identified a variety of determinants of teacher OCB, such as the school principal, the teacher's character, and the school's climate. Conclusions: Empirical and practical implications for the educational system and the educational research are suggested. Principals are strongly encouraged to establish a school environment that promotes OCB-oriented teachers and to create workshops to help him or her in this task. Researchers of educational systems are provided with new directions for research on the teacher's role and behavior. (Contains 2 tables.)