AbstractPublic perspective has long been ignored in ex-post evaluation of large cross-regional projects (LCPs), and the emergence of online public participation affords the opportunity to obtain and analyze public opinions from a wide range. Taking the South-to-North Water Diversion Project (SNWDP) as a typical LCP case, this study explored in depth the diverse and regionalized impacts of the project as reflected in online public opinion by developing an evaluation framework integrating post intensity, sentiment, and topic analyses. Leveraging lexicon-based sentiment analysis and latent Dirichlet allocation–based topic modeling technologies, patterns of public sentiments and topics were identified from spatial and temporal perspectives. The results showed that post intensity and public sentiment were significantly affected by project-related major events. A comparison of the water-donating and -receiving areas suggested that people in the water-receiving area had a more attentive and active attitude toward the project, and those in the water-donating area were predisposed to be more vigilant to negative events. Moreover, the variation of public sentiment across regions was found to largely depend on local social context. With regard to topic analysis, people in the water-donating and -receiving areas were more likely to focus on topics directly associated with their own interests, while the feasibility of the SNWDP garnered attention from both areas. In addition, project functions and significance as well as topical issues related to engineering corruption, water pollution, and security aroused widespread attention in all the areas under study. This study contributes to the literature on ex-post evaluation and public participation in the context of LCPs by incorporating online public opinion into the evaluation framework. The findings provide valuable insights for developing policies and strategies to improve the management of projects and to achieve an inclusive development process for projects of this type.