We develop and test a model that builds directly on social exchange theory to predict different roles for supervisor trust in the relationships between organizational citizenship behavior and relationship conflict occurring between supervisors and subordinates and between peers. Specifically, we posit that the association between citizenship behavior and relationship conflict between employees and supervisors is mediated by supervisor trust, while the association between citizenship behaviors and relationship conflict occurring between peers is moderated by supervisor trust. We test our dual role for supervisor trust in a field study of 160 supervisor–employee dyads. Results support the different roles played by supervisor trust. We close by discussing the implications of our results for theory and practice in the relationship conflict and citizenship domains.