Through a qualitative case study, this study explores why enterprise social media is used for knowledge sharing among information professionals, and what factors drive and hinder sharing knowledge on enterprise social media among information professionals. Data was collected through online semi-structured interviews with seven information professionals based in a Scandinavian country. Qualitative analysis of content was used in this study and the results were analyzed according to the affordances of enterprise social media of visibility, persistence and association, and related to previous research. The study concludes that information professionals use enterprise social media for knowledge sharing to increase their professional development, and there are diverse factors influencing knowledge sharing on enterprise social media. Some significant drivers to knowledge sharing are helping others and develop expertise. Significant barriers are fear of sharing and lack of trust in content. The outcome of this study gives a better understanding of why information professionals use enterprise social media for knowledge sharing and what factors influence their knowledge sharing practices on enterprise social media.