The aim of the study was to investigate the efficiency of adsorptive removal of nitrate from model aqueous solutions using chemically modified brewers' spent grain, a lignocellulosic by-product of beer production, as adsorbent. The applicability of the modified brewers' spent grain as adsorbent was evaluated in batch adsorption experiments, whereas the effect of different parameters on the adsorption efficiency was investigated. Namely, mass concentration of adsorbent (1 - 8 g/L), adsorption time (1 - 1440 min), initial mass concentration of nitrate (25 - 200 mg/L) and pH (2 - 12). The adsorption efficiency, i.e. the percentage of nitrate removal, was greater than 60% in all the experiments performed (60% to 100%). The percentage of nitrate removal was increased by increasing the mass concentration of the adsorbent and extending the contact time between the adsorbent and the adsorbate. An increase in the initial mass concentration of nitrate led to a decrease in the efficiency of the adsorption process, whereas pH had no significant effect on the adsorption efficiency (except in the case of pH value 12). The experimental data obtained from batch adsorption experiments were analysed using the Freundlich and Langmuir equilibrium adsorption models and it was concluded that both models well describe the nitrate adsorption process on the modified brewers' spent grain. Analysis of the data using kinetic models showed that the above adsorption process is well described by the pseudo-second order model and that intracellular diffusion is not the only step limiting the diffusion process. The chemically modified brewers' spent grain has been successfully used as an adsorbent for the removal of nitrates from aqueous solutions.