Although there is interest on educational leadership in Spain, research has focused on principal leadership and little has been investigated about teacher leadership. In the context of the International Study on Teacher Leadership (ISTL), this study aims to develop understanding of the concept of teacher leadership in institutional documents in Spain and to explore and analyze the dominant values and assumptions that can be identified. The review of the documents revealed a limited understanding of the critical importance of teacher leadership. Findings identified some aspects in the teacher leadership literature reviewed such as teamwork, accountability, openness to change, reflection, and advocacy, whereas inclusiveness, risk-taking, shared vision, and stability are scarcely identified. The increasing emphasis on teacher leadership dimensions in recent institutional documents note the need to go further with support for teachers' secondary roles as a consequence of the required modernization of the teaching profession.