Purpose: The current study aims to evaluate the water quality of the Tlawng river for both pre-treated and treated water. The Tlawng river is an important river to study since the residents of Mizoram's capital city, Aizawl, rely significantly on its discharge for drinking water. The Tlawng river also has significance for research because it transports biomedical effluents from Civil Hospital and Ebenezer Hospital. Methodology: Seasonal studies were conducted on a range of physico-chemical properties (pre-monsoon, monsoon, and post-monsoon seasons). The analysis was conducted using the procedure described in "Standard Methods for Examination of Water and Wastewater." The results were contrasted with scientific standards set by organisations like the World Health Organisation (WHO), the Indian Council of Medical Research (ICMR), the Bureau of Indian Standards (BIS), and the United States of Public Health (USPH). Results: With the exception of pre-treated turbidity and alkalinity, all of the physicochemical parameters tested during the study period were found to be within the acceptable range. Electrical Conductivity and Total Dissolved Solids levels were found to be higher during the pre-monsoon season, which could be attributed to inadequate water availability from sources, increasing salt concentrations, and the leaching of various pollutants and micronutrients from groundwater. Turbidity and acidity have higher values during the monsoon season, which is associated with heavy rainfall that washes adjacent fertilised agricultural fields, city waste, and other contaminants into river bodies of water. It was also found that the pre-monsoon season had increased total hardness and alkalinity. This might be attributed to a number of factors, including low water tables, water evaporation, and activities like bathing and cleaning along the bank using soap or detergent that contains alkalinity- and hardness-causing compounds. Conclusion: This study revealed the importance of taking serious management activities and methods to protect, conserve, and manage the Tlawng river. It is not recommended to drink water directly from the Tlawng river without treatment. It is vital to investigate the Tlawng river's water quality before an emergency occurs.