The purpose of this study is to investigate the role of school principal trustworthiness components (i.e., ability, integrity, benevolence) in helping shape teacher trust and affective commitment within schools. Using data from 1,026 teachers in Spain and structural equation modeling (via EQS 6.3), this study establishes how a principal's integrity and benevolence are key in determining, both directly and indirectly (via trust in the principal), teachers' affective commitment to their school. It also reveals that the perceived ability of a principal is not effective in generating trust or affective commitment to the school in teachers. As a contribution to the literature, these findings reveal that the ethical trustworthiness (benevolence, integrity) of principals is key in engendering trust and affective commitment to schools. Thus, to shape work environments that are high in trust and commitment, principals should focus on behaving in ways that make their integrity and benevolence manifest to their teachers.