The adsorption behavior of nitrate nitrogen was investigated from aqueous solution using char prepared from oak chip. The removal rate of nitrate nitrogen was found to be dependent on temperature and it is increased as the temperature increase. Adsorption equilibrium data of nitrate nitrogen on oak char. reasonably fitted Langmuir and Freundlich isotherm models. The adsorption energy obtained from D-R model was 12.5 kJ/mole at $20^{circ}C$ indicating an ion exchange process as primary adsorption mechanism. Thermodynamic parameters such as ${Delta}G^o$, ${Delta}H^o$, and ${Delta}S^o$ were -23.76 kJ/mole, 26.1 kJ/mole and 89.7 J/K mole at $20^{circ}C$, respectively, indicated that the nature of nitrate nitrogen adsorption is spontaneous and endothermic.