Improving export resilience has become a pivotal factor in navigating ongoing transformations in the global trade landscape, which are characterized by escalating geopolitical conflicts, accelerated supply chain restructuring, and rising trade protectionism. It is therefore essential to advance the high-quality development of China's foreign trade and consolidate its competitive position in the global trade system. From the perspective of informal institutions, this study investigates the mechanisms through which social capital influences export resilience, given that social capital, as a core carrier of informal institutions, plays a crucial role in reducing transaction costs and facilitating resource flow. Using panel data from 30 Chinese provinces and municipalities covering the period 2009–2022, regional export resilience is measured through using the Hodrick–Prescott (HP) filter, which effectively quantifies recovery capacity and fluctuation adjustment capacity by separating the trend and fluctuation components of export growth. Social capital levels are measured using the entropy method, an objective weighting approach covering cognitive, bonding, and linking dimensions to avoid subjective biases. Empirical analyses are then conducted to examine the impact and underlying pathways of social capital on export resilience, with control variables such as openness, government intervention, and financial development included to enhance reliability. The results show that social capital significantly enhances export resilience, and this finding remains robust under stability tests that including core variable replacement and endogeneity control. The mechanism analysis further reveals that industrial upgrading and innovation capacity serve as key mediating mechanisms. Moreover, the heterogeneity analysis demonstrates that the influence of social capital varies considerably across regions at different levels of economic development. The effects of individual dimensions of social capital also exhibit differentiation. Based on these findings, this study proposes targeted policy recommendations, including fostering and guiding the development of social capital, providing differentiated support for various type of social capital, and establishing cross-regional experience-sharing mechanisms to enhance China's overall export resilience.