The purpose of this research is to examine the mediating role of organizational culture in the effect of school principals' authentic leadership behaviors on teachers' organizational citizenship behaviors. The research was conducted with 300 teachers working in the Pendik district of Istanbul province in the 2020-2021 Academic Year. Authentic leadership scale, organizational culture scale, and organizational citizenship level scale were used in the research. According to the research findings, school principals' authentic leadership behavior level, teachers' organizational citizenship behavior levels, and organizational culture levels were high. Authentic leadership's organizational citizenship behavior is 8%; It was found that it affects organizational culture by 61%. It has been concluded that organizational culture has a fully mediating role in the effect of authentic leadership on organizational citizenship behavior.