Systems thinking (ST) is a holistic leadership approach that puts the study of wholes before that of parts. It focuses attention on how organization members act together in networks of interactions. This is done by researching organization members' mental models, which are deeply ingrained assumptions, generalizations, or even mental pictures or images that influence how one understands the world and thus takes action in order to achieve desired results. The purpose of this study was to explore the ST of school management teams (SMTs) through mental models. The main research question leading this inquiry was: How does ST reflect and express the mental models of SMTs? Qualitative data were collected via structured open questions. Hundred and fifty-four SMT members who worked at different school levels participated in this study. Data analysis was conducted by generating themes through an inductive process of condensing, coding, categorizing, and theorizing. The data analysis yielded five major themes: (a) the nature of teamwork; (b) shaping schools' goals and policies; (c) systemic gathering of information; (d) shaping the pedagogical work; and (e) decision-making and problem-solving as one organic puzzle. These themes were found to be closely interrelated in the context of schoolwork. This study highlights the importance of understanding more fully the role of SMTs' ST in schools. The study proposes that SMT members focus on ST characteristics that can enhance overall effectiveness. This can help SMTs achieve better cooperation with their counterparts as a leverage for school effectiveness.