Objective To investigate the microstructural and hemodynamic characteristics of the temporal lobes following radiation therapy in nasopharyngeal carcinoma patients with normal MRI manifestations. Methods Diffusion tensor imaging (DTI) and dynamic susceptibility contrast-enhanced perfusion MR imaging (DSCE-MR) were performed in 56 nasopharyngeal carcinoma patients, including 14 pre-radiotherapy patients (control group) and 42 post-radiotherapy patients; the latter was evenly divided into 3 groups: Group 1 (0-6 months after radiation therapy), Group 2 (6-12 months after radiation therapy), and Group 3 (>12 months after radiation therapy). The fractional anisotropy (FA) and relative cerebral blood flow (rCBF) were calculated in bilateral temporal lobes before and after radiotherapy. One-way analysis of variance (one-way ANOVA) test was used for comparison among groups. Results The FA values of the pre-radiation and three post-radiation groups were 0.48±0.04, 0.37±0.03, 0.42±0.04, and 0.43±0.03, respectively, showing significant difference among groups (F=13.897, P<0.01). Multiple comparisons showed that the FA values in the three post-radiation groups were significantly decreased compared with that in the pre-radiation group (P<0.05 or P<0.01). The FA values in Group 2 and Group 3 were higher than that in Group 1 (P<0.05 or P<0.01). The mean rCBF values of the pre-radiation and the three post-radiation groups were 23.21±3.67, 17.56±3.01, 18.58±3.48, and 20.34±2.59, respectively, showing significant difference among groups (F=8.714,P<0.01). The rCBF values in the three post-radiation groups were significantly decreased compared to that in the pre-radiation group (P<0.05 or P<0.01). And the rCBF value in Group 3 was significantly higher than that in Group 1 (P<0.05). Conclusion DTI and DSCE perfusion MRI can detect micro-injury of brain tissue and can be used for early monitoring and evaluation of radiation-induced injury. Blood vessel injury may have participated in the early radiotherapy-induced brain injury.