This study conducted an analysis to determine the impact of social capital, which is the sum of resources embedded in a company's external network, and diversification strategy, which is a specific implementation tool to achieve performance goals, on export performance from the perspective of supply chain partnerships. Structural capital and relational capital of social capital were set as potential variables, and the diversification strategy was classified into product diversification strategy and market diversification strategy, and then a research model was built to examine each causal relationship on the path to export performance. And a total of eight hypotheses were established. Empirical analysis was conducted using the PLS (Partial Least Squares) structural equation model with a sample of a total of 244 small and medium-sized export manufacturers collected through a survey. As a result of the analysis, both structural capital and relational capital showed a positive relationship with product diversification strategy and market diversification strategy, so Hypotheses 1 to 4 were adopted. However, since neither structural capital nor relational capital had a significant effect on export performance, Hypotheses 5 and 6 were rejected. Product diversification strategy was not significant on export performance, so Hypothesis 7 was rejected. However, market diversification strategy was found to have a positive effect on export performance, so Hypothesis 8 was adopted. Based on these analysis results, theoretical differences from previous studies were presented, practical implications were derived, and future research directions were suggested.