The present study was conducted to assess the physicochemical characteristics of water quality parameters concentrations in water at different locations of the Karnafuli River. The assessment was carried out for various physicochemical parameters in three seasons during pre-monsoon, monsoon and post-monsoon seasons for various continuous monitoring during the hydrological year 2014-2015. The statistical methods of sampling were used for collecting samples from different points of Karnafuli River. The samples were collected in high and low tide conditions. Since the water quality is expected to vary with season, multiple samples were collected at an interval of 2 to 3 weeks. The work has been carried out by traveling to the sampling sites for collection required water samples and the estimation of water discharge and determination of basic parameters of the sites. Samples were preserved with suitable preservation and transported to the laboratory. Standard methods were followed to determine the physicochemical water quality parameters. In the present study, seasonal variation hydro-chemical character of Karnafuli River water has been evaluated and assessed the suitability of water for human & animal′s consumption, irrigation and industrial purposes. The study stress to access various essential physical and chemical parameters including pH, conductivity, salinity, total dissolved solid (TDS), total suspended solid (TSS), turbidity, alkalinity, acidity, dissolved oxygen (DO), sulfate, biological oxygen demand (BOD), Chemical demand oxygen (COD), nitrate, phosphate, chloride, total- hardness. The average of maximum parameters studied both physical and chemical were found higher than those of the World Health Organization( WHO), Department of Environment (DoE) and BSTI drinking water guidelines. The laboratory finding of water quality parameters were also compared with the recommended values set by DoE and BSTI. From Pearson correlation program, significant positive and negative correlations were found in different parameters. These assessment data indicated that the water quality of Karnafuli River are highly polluted which are continuously polluting the coastal zone, sea and the Halda River of Chittagong. The environmental impact of water quality of Karnafuli River has been discussed. The result provided data to understand and quantify the threat of the impact of climate change on river water resources of greater Chittagong region. The result also provided data for water quality of Karnafuli River water resources of greater Chittagong region to match national and international standard for drinking, agriculture, industrial and livestock requirements. The assessment data can be used to help the determination the efficacy of existing water quality policies to help analysts determine the need for and likely consequences of new policies. The assessment data can be supplied to the proper Govt. authority for making new national and appropriate preventive measures. The assessment can be increased the awareness of the people of the risk and affected areas so that they could ready to face the disaster due to climate change, from the investigation it can be concluded that the water quality of Karnafuli River is being affected by pollution hazard. The delay of the application of the legal frame work as well as stakeholder awareness aggravates the situation by continually reducing the water quality in the river. A strategic water quality management plan has been proposed.