We investigated the combined effects of temperature and X-rays exposures on the nature of point defects generated in Ge-doped multimode optical fibers. Electron paramagnetic resonance (EPR) results on samples X-ray irradiated at 5 kGy(SiO2), employing different temperatures and dose rates, are reported and discussed. The data highlight the generation of the Ge(1), Ge(2), E0 Ge and E0 Si defects. For the Ge(1) and Ge(2), we observed a decrease in the induced defect concentrations for irradiation temperatures higher than *450 K, whereas the E0 defects feature an opposite tendency. The comparison with previous post-irradiation thermal treatments reveals peculiar effects of the temperature increase during the irradiation. Such difference, confirmed also by online radiation-induced attenuation measurements, has to be considered for practical use of these fibers in a mixed environment. Importantly, even if post-irradiation fading should be considered, the Ge(1) and Ge(2) concentrations measured by post-mortem EPR experiments in room-temperature-irradiated samples are quite representative of the concentrations induced in the temperature range 230–450 K regardless of the investigated dose rate. The enhancement of the E0 content can be related to the simultaneous generation of this defect with non-bridging oxygen hole center from strained bonds implying a relevant modification of the defects generation/formation processes in the host glass matrix