To date, hydropower dams raise numerous interpretations about their impact on the Lancang-Mekong River. While most research studies analyze the negative aspects of hydropower development on people’s livelihoods and local environments, the hydropower sector was historically one of the most iconic economic segments facilitating transboundary water cooperation for decades. By using the constructive discourse analysis and critical political ecology approach, the presented text (1) outlines the current environmental narratives over the Lancang-Mekong hydropower development and (2) explores the politicization of the Chinese mainstream dams. The data were collected upon the multi-level content analysis of relevant sources and double-checked with the Lancang-Mekong Cooperation and Conflict Database (LMCCD) monitoring over 4000 water-related events among six riparian countries between 1990 and 2021. Our data show that (i) there is a stark contrast in positive and negative narratives over the rapid hydropower development, (ii) the impact of mainstream dams on the river is more often discussed than that of tributary dams, (iii) implications of the hydropower dams are often interpreted upon the non-traditional research inputs rather than widely accepted studies, and (iv) developing the contradictory arguments through social and public media contributes to greater polarization of the multi-stakeholders’ viewpoints in the accountable research dialogue.