Budget management is a cornerstone for achieving high-quality and modernized economic development in China. As a critical component of budget systems, budget slack is influenced by multiple factors, among which the intellectual capital formed by executives’ overseas backgrounds has become a focal point for corporate discussion. This study uses data from A-share listed companies in Shanghai and Shenzhen from 2016 to 2022 to examine the impact of executives’ overseas backgrounds on corporate budget slack from the perspective of risk-taking, further exploring the moderating role of environmental uncertainty in this relationship. The results show that executives’ overseas backgrounds can inhibit corporate budget slack by enhancing the level of corporate risk-taking. Environmental uncertainty exhibits a complementary effect in the relationship between executives’ overseas backgrounds and budget slack. Heterogeneity analysis reveals that the impact of executives’ overseas backgrounds on budget slack is more pronounced in non-state-owned enterprises, small-scale enterprises, and enterprises with weaker external oversight.