Past research has long emphasized the critical roles of approach and avoidance motivation orientations in people’s creative and innovative performance. However, it has generated mixed results and suggested the possibility of multiple pathways and mechanisms to explain these relationships. In this article, we first argue that employees’ approach and avoidance motivation orientations are likely to guide their knowledge-sharing (KS) behaviors, which, in turn, influence their innovative performance. We differentiate between explicit and implicit KS and posit that approach motivation orientation is positively associated with both types of KS. In addition, we argue that while avoidance motivation orientation is positively related to explicit KS, it is negatively related to implicit KS. From a support–threat perspective, we also propose that perceived organizational support and psychological contract breach moderate the effects of approach and avoidance motivation orientations, respectively. We tested these relationships in a survey of 331 employees and their supervisors in two organizations in China. The results supported all of the hypothesized relationships, except for the relationship between avoidance motivation orientation and explicit KS, which was only significant when psychological contract breach was lower. These findings have both theoretical and practical implications.