Background <p>Political corruption undermines the effectiveness of environmental governance by eroding institutional capacity, distorting regulatory frameworks, and weakening policy enforcement. This study revisits the relationship between political corruption and environmental policy stringency (EPS), focusing on how corruption influences the strength of environmental regulations across countries and over time.</p> Methods <p>A cross-national time-series analysis is conducted for 40 countries from 1990 to 2020 using data from the V-Dem Political Corruption Index and the OECD Environmental Policy Stringency Index. The baseline estimation employs a two-way fixed-effects model, complemented by robustness checks using Panel-Corrected Standard Errors (PCSE), Feasible Generalized Least Squares (FGLS), and System Generalized Method of Moments (System GMM).</p> Findings <p>Results consistently demonstrate that higher political corruption is significantly associated with lower environmental policy stringency. Corruption weakens institutional oversight and enforcement capacity, thereby reducing governments’ ability to implement stringent regulations. Unexpectedly, the negative effect of corruption is more pronounced in developed countries, likely reflecting subtler, institutionalized forms such as regulatory capture and corporate lobbying.</p> Conclusions <p>While institutional maturity can limit overt corruption, it does not fully shield advanced economies from its environmental consequences. These findings highlight that anti-corruption reforms should be integral to strategies for strengthening environmental governance.</p>