Enterprise social media platforms (ESMPs) are web 2.0-based computer media tools that facilitate knowledge sharing by employees. The purpose of this paper is to outline the potential of ESMPs in both enabling and hindering knowledge sharing from the perspective of affordances. Design/methodology/approach This is a conceptual paper which integrates the literature on ESMPs’ affordances and knowledge sharing. Findings This paper finds that prior research on affordances only considered artifacts without much attention on the role of individual goals and organizational context. ESMPs may both enable and hinder knowledge sharing by affording different user behaviors contingent on artifacts, individual goals and organizational context. Practical implications The results of the paper will help managers and ESMPs designers to better understand the potential of ESMPs and pay attention to the positive and negative impacts of ESMPs in the process of knowledge sharing. Originality/value The paper derives a new categorization of affordances based on individual goals and organization context and portrays a model to describe how and when these affordances enable knowledge sharing through the development of transactive memory system and social capital and hinder knowledge sharing through overload, groupthink and privacy invasion.