Drawing on organizational learning and the relational view of the firm, this study seeks to understand the factors that drive supplier innovativeness in the context of cross-border supply relationships. To address this research objective, a survey included 189 parts and components manufacturers (suppliers) in Turkey; hierarchical regression analysis is used to test the hypotheses. The findings demonstrate that interfirm knowledge sharing routines, relation-specific investments, and governance mechanisms may promote supplier innovativeness by expanding the supplier's knowledge resources and encouraging it to invest in innovative activities. In addition, this research emphasizes differentiating effects of the supplier's tier position for the impacts of buyer assistance and cooperative tie. As such, this study contributes to the purchasing and supply management literature by empirically showing how buyer–supplier relationships, particularly in cross-border supply networks, affect supplier innovativeness.