The irradiation hardening of the Eurofer97 steel following 590 MeV proton irradiations was determined at three different irradiation temperatures, 50 °C, 250 °C and 350 °C, and various doses up to about 1.3 displacement per atom. The dose and temperature dependence of the irradiation hardening was characterized by a linear relationship between the irradiation hardening and the square root of the dose as: Δ σ 0.2 = k( T) dpa 1/2. Mini pre-cracked bend bar (1 × 1 × 16 mm 3) were also tested in the lower ductile to brittle transition region before and after irradiation at 300 °C and 0.5 dpa. The effective fracture toughness-temperature curves, K e( T), were indexed on an absolute temperature scale at T 0 for K e = 100 MPa m 1/2 for both the unirradiated and irradiated condition. The irradiation-induced temperature shift Δ T 0 of the K e( T) curves yielded a coefficient C 0, defined as C 0 = Δ T 0/Δ σ 0.2, of about 0.53. For these low doses, helium effects could not be identified on the fracture properties.