The COVID-19 pandemic has badly affected the global economy. The use of social capital as a resource to diversify agribusiness to get more customers and improve the agricultural supply chain is a considerable issue to explore. This study aims to develop a comprehensive measurement of social capital and examine its effect on the intention to diversify agribusiness. From a supply chain perspective, it uses theory of planned behavior (TPB) and resource-based view (RBV). An integrative measurement scale of social capital from an agricultural supply chain perspective is suggested. The study also shows significant causal relationships amongst social capital, motives, TPB's determinants and the intention to diversify agribusinesses in light of supply chain perspectives. The study offers a significant contribution to the existing body of knowledge in the literature on social capital, motives, TPB, RBV and supply chain perspectives. The study was executed in Vietnam, where most farmers are smallholders, family business owners or micro-scale entrepreneurs in agriculture.