This article aims to construct and empirically verify a model that demonstrates the association between social capital dimensions, knowledge sharing, and firm performance. For data collection, a questionnaire was delivered to medium and small enterprises across Ho Chi Minh City using convenience sampling. To verify the proposed relationships, the data collected from 543 middle and top managers of medium and small enterprises were then examined using Structural Equation Modelling. Overall, explicit and tacit knowledge sharing are fostered as a result of all social capital dimensions. In a similar vein, both types of knowledge sharing influence firm performance. The study proposes a guide as to how firms should achieve better performance by promoting social capital and knowledge sharing.