This article presents empirical information on experiences of corruption in the wastewater sector. Previous studies have examined the types and magnitude of corrupt behaviour that have been documented in water supply and sanitation services and have found that corruption in the sector is sophisticated and pervasive. Drawing on interviews with key stakeholders, we document a range of corrupt behaviours at the citizen–institution interface and in public financial management. Our findings underline the importance of contextual factors, including the rapid industrialisation and urbanisation taking place in the Extended Bangkok Metropolitan Region, as well as the existing institutional and regulatory weaknesses. Our findings also point to the environmental impact of corruption in the wastewater sector, a hitherto neglected factor which our respondents perceived as an immediate and direct threat to their communities and livelihoods.