Most research on trust in interorganizational relationships focuses on a single level of analysis, typically the individual or organizational level, and treats trust as a fairly static phenomenon. To stimulate more cross-level research, we propose a theoretical model that explains how trust in interorganizational relationships is related across various levels of analysis. At the same time, our model emphasizes the dynamic aspect of trust by examining how trust develops throughout consecutive relationship stages. Drawing from several programs of research, we identify the mechanisms that drive the progression of trust across levels as the interorganizational relationship unfolds. Starting with the boundary spanner as the key individual at the beginning of a new collaboration, we specify how trust gradually becomes part of the fabric of organizational action. By integrating micro and macro approaches over time, the proposed model contributes to a better understanding of how trust evolves in interorganizational relationships.