<italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>Background:</b></i> Social media has transformed communication in professional settings, giving rise to the social commerce sector. However, its impact on employee performance remains unclear, limiting its application efficiency. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>Literature review:</b></i> Prior research presents varied findings on how social media influences work performance. This issue in the social commerce sector remains ambiguous. Most studies focus on either the benefits or risks of social media, neglecting a comprehensive view. In addition, the role of guanxi in promoting knowledge-sharing behaviors is underexplored. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>Research questions:</b></i> 1. What is the impact of social media use on employee performance in the social commerce industry? 2. How does social media use affect employee performance through knowledge-sharing and technostress? 3. How does guanxi moderate the relationship between social media use and knowledge-sharing behaviors and consequently on employee performance? <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>Methodology:</b></i> We surveyed 520 Chinese social commerce professionals, using self-reported questionnaires to investigate how social media use affects employee performance. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>Results:</b></i> Social media positively impacts job performance, with benefits outweighing drawbacks. It enhances knowledge-sharing behaviors which, in turn, improves employee performance. It also causes five technostress factors, but only techno-overload and techno-uncertainty significantly reduce employee performance. In addition, guanxi moderates the relationship between social media use and knowledge-sharing behaviors and strengthens the indirect effect of social media use on work performance through knowledge-sharing. However, this moderated mediation effect is not significant at low levels of guanxi. <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><b>Conclusion:</b></i> The results can help organizations effectively leverage social media as a valuable communication tool by fostering guanxi, promoting knowledge-sharing, and managing specific technostress factors.