Manufacturing firms that outsource customer-facing services, risk losing touch with their customers and thereby forfeit valuable market and customer-related knowledge. To maintain informed and competitive, the manufacturer's customer-facing service partners should engage in knowledge sharing and transfer their market knowledge and insight to the firm. Building on knowledge transfer and organizational learning theory, this study investigates how contractual and non-contractual (i.e., relationship) characteristics influence knowledge sharing behavior by service partners. The authors specifically distinguish between sharing exploitative knowledge (insights that help the manufacturing firm to refine current skills and procedures) and exploratory knowledge (insights that help the manufacturing firm to challenge prior approaches to interfacing with the market). Based on survey data from 70 relationship managers from a large multinational firm and partial least squares path modeling, results show that contractual incentives had a negative effect on exploratory knowledge sharing, but not on exploitative knowledge sharing. The level of contract specification and relationship quality positively related to both types of knowledge sharing. Relationship manager experience related positively to exploratory knowledge sharing, but not to exploitative knowledge sharing. These findings provide valuable insights on how (non-)contractual mechanisms can be used to manage knowledge sharing in outsourced services.