PurposeOrganizations use enterprise social media (ESM) platforms to operate, function, and develop. However, the effectiveness of the use of ESM is inconclusive. This study aims to explore the mechanism and boundary conditions of the relationship between employee ESM use and job performance.Design/methodology/approachThis study uses a 2-wave survey design, with a final sample of 481 employees from a large automobile company.FindingsThe results indicate that ESM use is beneficial and detrimental to job performance. On the one hand, ESM use is positively related to work overload, decreasing job performance. On the other hand, ESM use is positively associated with informational support, increasing job performance. A mediation test revealed that both work overload and informational support mediate the relationship between ESM use and job performance. Furthermore, job autonomy weakens the positive relationship between ESM use and work overload, but strengthens the positive relationship between ESM use and informational support.Originality/valueThis study provides a more balanced view of how ESM use influences job performance by demonstrating the opposing mediating roles of work overload and informational support. Further, this study fills a research gap by considering job characteristics when examining the boundary conditions of ESM use. Third, this study validates the generalization of the job demands-resources model in social media research.