This research investigated the evolution of tensile, hardness, and fracture properties of Eurofer97 tempered martensitic steel following neutron irradiation. The irradiation-hardening was measured with Vickers hardness tests on broken parts of sub-sized compact tension specimens as well as with tensile tests deformed at room temperature. The fracture toughness was measured with pre-cracked sub-sized 0.18T compact tension specimens. Two specimen sets were irradiated up to a nominal dose of about 0.35 dpa at two different temperatures, 423 and 623 K, in the experimental reactor at AEKI-KFKI in Budapest. The median fracture toughness-temperature curve K(T) was characterized in the lower to middle transition region for each irradiation condition using the master-curve method. The irradiation-induced temperature shifts of K(T) were determined by calculating the reference temperature T-0 at which the median toughness is 100 MPa m(1/2). A significantly larger shift was determined for Eurofer97 irradiated at 423 K than at 623 K. Indeed, an upper shift of 98 K was found for the 423 K irradiation while only 50 K was measured for the 623 K. On the one hand, that observation reflects the difference in the irradiation-hardening following those two irradiation temperatures. On the other hand, when compared with other published data, the Delta T-0 shift at 623 K irradiation was found to be greater than expected for the corresponding irradiation-hardening. Thus, it was suggested that non-hardening embrittlement mechanisms start to operate around 623 K. (C) 2013 Elsevier B. V. All rights reserved.