There is ample evidence indicating that political institutions and official mobility influence the economy, finance, and environment. Specifically, political turnovers have been found to be essential for the functioning and oversight of economic institutions. Chinese cities, where the party secretary frequently changes every few years, provide an interesting context for studying political turnovers. In this study, we investigated the effects of political turnovers on urban sewage discharge in 242 Chinese cities between 2003 and 2018. The findings revealed a significant impact of the timing of the Chinese Communist Party Congress on urban sewage discharge. Leading up to and including the year of the Party Congress, there was a marked reduction in urban sewage discharge. Conversely, discharge increased substantially during the year or two years following the Party Congress. These results suggest that political turnovers play a critical role in environmental governance performance in China.