<p>Under China’s government-oriented environmental governance, the environmental impacts of political systems have gained prominence. Official turnover, a key political event, serves as a new entry point for studying political factors affecting the environment. This study uses a quasi-natural experiment design and empirical methods to examine the short-term “window effect” of official turnover on regional environmental performance. Results show official turnover causes temporary regulatory lapses, enabling firms to illegally discharge pollutants and degrade local environments in the short-term. Heterogeneity analysis reveals sharper regulatory disruptions and faster environmental decline when predecessors depart due to disciplinary investigations or successors are externally transferred. The paper’s core innovation lies in the short-term window effect of official turnover events themselves, contrasting with existing research, which examines medium-to-long-term effects and mixes factors, such as new officials’ governance styles and local policies, rather than focusing on the impact of the turnover event itself. This research provides a new explanatory mechanism for the environmental effects of official turnover, offering practical insights for local governments aiming to address corporate environmental opportunism and advance modern environmental governance.</p>