The Kobadak River system in southwestern Bangladesh faces significant social and environmental challenges due to water-logging. The study evaluated and assessed project performance and impact by comparing pre-project and study period indicators across multiple resource categories using both quantitative and qualitative methods, primarily employing percentage changes and absolute differences. Following the intervention, around 75,000 ha of land were reclaimed, and cropping intensity rose from 206% to 218%. The area of culture fish habitats expanded markedly, increasing from 3,825 to 19,962 ha. Enhanced drainage improvements also contributed to better road infrastructure and navigability, thereby facilitating transportation, trade, and communication, which in turn supported improved livelihoods. Economic assessments indicate robust financial gains, with a benefit-cost ratio of 14.6 and an estimated annual contribution of approximately Tk. 7.2 billion to the national GDP, highlighting the project’s positive socio-economic and environmental impacts. The findings demonstrate the effectiveness of the BWDB project and suggest measures to further strengthen its outcomes.