<p>Suitable irrigation water is essential for sustainable agriculture. However, rapid urbanization, industrialization, and population growth degrade water resources and trim down water quality for agriculture globally. The East Kolkata Wetlands (EKW) present a distinctive model in which untreated sewage water from Kolkata is utilized for downstream agriculture, thereby supporting nutrient recycling through wastewater reuse. This study evaluates the suitability of urban wastewater for irrigation in the EKW and investigates its spatial and temporal variations. The results indicate that, according to the Wilcox diagram, 46.15% of pre-monsoon and 53.85% of post-monsoon water samples fall within the excellent category for irrigation suitability. Additionally, 23.08% of pre-monsoon and 15.38% of post-monsoon samples are categorized as good, while 30.77% of samples in both seasons range between excellent and good categories. As per the United States Salinity Laboratory (USSL) diagram, 46.15% of pre-monsoon and 53.85% of post-monsoon samples are in the medium salinity and low sodium categories. Conversely, 53.85% of pre-monsoon samples and 46.15% of post-monsoon samples were found with high salinity and low sodium content. Irrigation indices further affirm that most water samples in this study are suitable for irrigation and raising crops. Entropy irrigation water quality index (EIWQI) analysis classifies 61.54% of samples as very good, 23.08% as good, 7.69% as average, and 7.69% as poor. Poor water is not recommended for irrigation, however, average-quality water should be monitored regularly for future risks. The analysis finds a potential in urban wastewater for urban agriculture, and it provides a basis for informed decision-making by water resource planners, agricultural administrators, and policymakers.</p>