Present work deals with the assessment of physico-chemical parameters of water samples of Kosi river at Kosi sampling station during 2004 and 2005 in pre monsoon, monsoon and post monsoon seasons. Statistical studies have been carried out by calculating correlation coefficients between different pairs of parameters and t- test applied for checking significance. The observed values of various physico-chemical parameters of water samples were compared with standard values recommended by WHO. It is found that an appreciable significant positive correlation holds for chloride with pH, Mg, Na, hardness and total suspended solid; and sodium with hardness, EC and sulphate. A significant negative correlation was found between potassium with turbidity, Cl-, EC and hardness. All the physicochemical parameters of Kosi water are within the highest desirable limit or maximum permissible limit set by WHO except turbidity and BOD which recorded a high value.