The purpose of this study is to explore the mechanism and boundary condition of the relationship between enterprise social media use and job performance. This study used a two-wave design, with a final sample of 481 employees from an automobile company. The results indicate that enterprise social media use is positively related to both work overload and informational support. Work overload and informational support predicts job performance negatively and positively, respectively. Furthermore, work overload and informational support mediates the relationship between enterprise social media use and job performance. Job autonomy moderates the relationship between enterprise social media use and work overload and informational support. Therefore, this study provides a more balanced view of how enterprise social media use influences job performance by demonstrating the opposing mediating roles of work overload and informational support. Furthermore, this study fills the gap by taking job characteristics into more consideration when examining the boundary condition of enterprise social media use. Last, this study validates the generalization of job demands-resources model in social media research.