Prior research provides evidence that manufacturer investments of specific assets dedicated to a particular supplier is an antecedent of joint action in manufacturer-supplier relationships. However, domain knowledge specificity surpasses physical asset specificity as an important determinant of governance choices in the knowledge-driven economy. This study focuses on the effect of supplier's investments of specific domain knowledge dedicated to a particular buyer on joint new product development in supplier-buyer relationships. Supplier's involvement in new product development depends on trust and commitment of the supplier. Drawing from transaction cost analysis and relational exchange theory, the author proposed a conceptual model that explicates the moderating role of a contextual variable: supplier's trust in buyer. Consistent with these hypotheses, results from a survey of firms in Taiwanese information industry show that trust enhances the effect of supplier domain knowledge specificity on new product development. The theoretical and managerial implications of the results are discussed.