This article examines the relationship between trust and the development of distributed leadership. It presents a theoretical argument with supporting evidence from longitudinal fieldwork examining distributed leadership development in comparative cases of two secondary schools. The analysis suggests that trust matters in the design, performance, and perceptions of distributed leadership; that the relationship between trust and distributed leadership development is dynamic and mutually reinforcing; that an initial level of positive or provisional trust may be necessary; and that principal leadership and the trust relationship between principal and teachers are especially important to distributed leadership development. (Contains 1 footnote.)