<p>Grounded in conservation of resources theory, this study examines how strain-related job stress is associated with employees’ innovative behavior through knowledge hiding and whether leader–member exchange quality weakens this indirect relationship. Drawing on two-wave time-lagged survey data from 496 employees in South Korea, we found that strain-related job stress was negatively associated with innovative behavior and positively associated with knowledge hiding. Knowledge hiding, in turn, was negatively associated with innovative behavior, partially mediating the relationship between strain-related job stress and innovative behavior. In addition, leader–member exchange quality moderated the relationship between strain-related job stress and knowledge hiding, such that the positive association was stronger when leader–member exchange quality was low rather than high. The conditional indirect relationship between strain-related job stress and innovative behavior through knowledge hiding was significant only under low leader–member exchange quality. These findings suggest that strain-related job stress may be associated with lower employee innovative behavior not only through internal resource depletion, but also through defensive regulation of knowledge access. The study contributes to research on job stress, knowledge hiding, and innovative behavior by identifying knowledge hiding as a social-behavioral pathway linking strain-related job stress to reduced innovative behavior and by highlighting high-quality leader–member exchange as a relational resource that may interrupt this pathway.</p>