This paper explores the degree to which social capital promotes sustainable performance. It also examines social capital’s influence on social, economic, and environmental performance. Data was collected drawing on a survey among a sample of 265 Tunisian manufacturing companies and estimated through the partial least squares (PLS). This research underscores the importance of social capital as a key determinant of sustainable performance and specifically of social, economic, and environmental performance. This research emphasizes how crucial it is for managers to strategically use social capital by striking a balance between strengthening and fostering relationships to improve sustainability outcomes. Businesses, particularly in resource-constrained countries, should make investments in robust internal networks to promote cooperation and trust, as well as growing external ties to gain access to a variety of expertise and resources, resulting in long-term sustainability and a competitive edge.