ABSTRACT As globalization and informatization progress, businesses have transitioned from solely pursuing economic interests to actively embracing social responsibility. However, in‐depth exploration of the marginal effect of urban policies on corporate social responsibility (CSR) disclosure is still relatively limited. This paper employs the establishment of cross‐border e‐commerce comprehensive pilot areas as a quasi‐natural experiment to investigate the impact of these policies on CSR disclosure and the underlying mechanisms. It is found that these policies significantly promote CSR disclosure by increasing industry competition and strengthening external supervision pressure. The heterogeneity analysis of grouping tests shows that the attributes of high‐tech and heavily polluting industries strengthen the policy effect. The generalized random forest algorithm reveals the conditional average treatment effect (CATE) of these policies and finds that firm characteristics do not exhibit a simple linear relationship with CATE. These findings offer theoretical and practical implications for policymakers and corporate managers aiming to foster sustainable business practices.