Trust is recognized as an essential component of efficient operation and well-functioning of school organizations. Studies of interpersonal trust related to schools suggest that the nature and quality of teachers' trust in principals contributes to important outcomes. In this sense, prior research has heavily focused on the attributes of the trustee and contextual factors, while neglecting the characteristics of the trustor. Thus, this study proposes an adult attachment style as personal characteristics of teachers developing trust in principals. The sample consists of 317 full-time primary and secondary teachers teaching in four private schools. Hierarchical regression analyses revealed that secure and preoccupied attachment styles were positively related to affective trust in principal, whereas none of the attachment styles were significantly related to cognitive trust in principal. The results of the study contribute to our understanding of the role of attachment styles in how teachers perceive and enact trust relationships at school.