Background: Radiation therapy (RT) is one of the common and successful treatments for brain malignancies and benign disorders. In spite of its irrefutable merits, it is associated with a number of complications caused by radiation damage to the important Organs at Risks (OARs), which is strongly correlated with the radiation dose during RT. This study aimed to determine the range of radiation dose to Hippocampus and certain OARs in the brain. Materials and Methods: Thirty-two patients with primary brain cancer, undergoing RT, were selected retrospectively. The selected OARs were contoured using the RT Treatment Planning Software through assessing the images from the computed tomography and magnetic resonance imaging (MRI). Dose parameters, namely maximum dose (Dmax) and median dose (Dmedian), to OARs (optic nerves, chiasm, retinas, lenses, orbits, lachrymal glands, brainstem, hippocampi, etc.) were assessed. Results: The mean age of the patients was 37.8±14.3 years (from 5 to 60 years), and 19 patients (59%) were male. Glioblastoma multiforme and astrocytoma were the most common tumors. The maximum dose received by the brainstem, lenses, and eye ranged between 32-62 Gy, 0.75-40 Gy, 1.5-65 Gy, respectively. The maximum dose received by the hippocampi was 62.7 Gy. Conclusion: Important OARs can tolerate the received doses which were lower than the threshold level of serious complications. However, the maximum dose received by the hippocampi was higher than the recommended tolerated radiation dose; therefore, it is recommended to conduct more studies in this regard.