Research on the sources of organizational trustworthiness remains bifurcated. Some scholars have adopted a calculative perspective, stressing the primacy of actors' rational calculations, while others have approached trustworthiness from a relational perspective, focusing on its social underpinnings. We help to reconcile these seemingly disparate views by adopting an integrative approach that allows us to clarify the boundaries of both perspectives. Based on dyadic survey data from 171 strategic alliances, we find that the calculative perspective (represented by contractual safeguards) has higher predictive power when the partner lacks a favorable reputation. In contrast, the relational perspective (represented by organizational culture) predicts trustworthiness more strongly when familiarity with the partner organization is high.