Abstract: Since social media increasingly infiltrates the workplace, it may affect employee innovation. However, how social media use (SMU) affects employee innovation performance remains controversial. Therefore, this study explores the underlying mechanisms and boundary conditions in the relationship between SMU and employee innovation performance. The research model was tested through a survey of 221 Chinese employees. The results show that SMU is positively related to employee innovation performance, with work engagement acting as a mediator in this relationship. Employee traditionality positively moderates the positive impact of work-related SMU on work engagement, while traditionality has no moderating effect on the relationship between social-related SMU and work engagement. This study focuses on the relationship between SMU and innovation performance based on conservation of resources theory, offering insights into the intrinsic mechanism by which SMU affects employee innovation. Furthermore, this study considers the moderating effect of employee traditionality based on social cognitive theory, enriching the knowledge of how traditionality influences the impacts of SMU. This study has theoretical implications for future research and practical guidance for enterprises regarding the proper use of social media.