Single crystals of NaBi(WO4)2 grown under different conditions were studied for their radiation hardness to high gamma radiation doses (105 and 106 Gy) employing high dose rates (∼2 Gy/s). Annealing studies in oxygen as well as in vacuum were carried out and a relation between oxygen defects and irradiation induced damages has been proposed. Induced absorption spectra of irradiated and annealed samples were calculated and 5 individual peaks around 3.1, 2.8, 2.6, 2 and 1.7 eV related to different defect centers have been identified. Recovery of the transmission characteristics after the heavy irradiation was monitored at room temperatures (20±2 °C) and the corresponding lifetime has been found to be about 50 days. The thermoluminescence glow curve has been recorded and the activation energy of the defect centers was calculated as 0.9 eV using an initial rising method. © 2010 Elsevier B.V. All rights reserved.