Hardness measurements and microstructure examinations of Fe(-C)-Cu-Ni model alloys were performed following 1 MeV proton irradiation below 80°C. Microstructural examinations by transmission electron microscope (TEM) were carried out by means of a cross section method. A band of damage structures, parallel to the irradiated surface, was observed at a depth of 6.5 μ m in agreement with calculation based on the TRIM code. TEM observation revealed that the band consisted of high density of small black spots, which were considered to be interstitial-type dislocation loops. The amount of irradiation hardening increased with increase in copper concentration. An addition of 0.6wt%Ni to Fe-Cu alloys further increased the hardening, although the effect was reduced with increasing copper concentration. Irradiation hardening of pure iron was also significantly increased by the addition of nickel. The size and number density of the spot-like structures in Fe-Cu alloys decreased and increased, respectively, with addition of nickel. Three recovery stages were found in Fe-Cu-Ni alloys during post-irradiation isochronal annealing to 675°C: the stages are at around 150°C, 400°C and 600°C. The first stage was only observed in nickel-containing alloys, while the third stage was only observed in copper-containing alloys. After annealing to 375°C, the density of spot-like structures decreased in Fe-Cu-Ni alloy but increased in Fe-Cu alloy, while for both the size of spots increased.