Purpose: Decades of research in educational leadership has extolled the importance of principals in both the effective functioning of teachers and the overall performance of schools. The mechanisms explaining what makes principals effective in the eyes of teachers, however, are not well known. This study builds on prior research to posit that principal effectiveness is the result of their own cognitions, which are translated into specific leadership behaviors directed at teachers, which, in turn, serve to foster trust. Research Methods/Approach: Data came from principals and teachers in 33 French and English Canadian elementary schools. All principals took part in a face-to-face interview which elicited their leadership cognitions, while teachers responded to measures of principal leadership behaviors, trust, and effectiveness. Findings: This research provides empirical support for a sequential mediation model whereby principal leadership cognitions were related to teacher evaluations of principal effectiveness through teacher ratings of principal leadership behaviors and teacher trust in their principal. Specifically, we found support for three specific leadership behaviors (supporting, developing, and active management-by-exception). Implications for Research and Practice: The results reveal the importance of a number of distinctive leadership behaviors in fostering a work context where teachers are able to perform effectively. Principals who "walk the talk" tended to be perceived as more trustworthy and effective. Additionally, the results suggest that principals' professional development could focus on cognitions related to leadership behaviors and effectiveness.