The results of superconducting transition investigations of intermetallic compound Nb 3Ge irradiated in superconducting state in the nuclear reactor cryochannel are presented. Superconducting transition temperature T c of the thin intermetallic layer (2 μm) deposited on the molybdenum wire of 0.5 mm diameter was determined by the resistivity method. It is shown that T c of Mo–Nb 3Ge composition changes insignificantly up to the fast neutron fluence ∼2.3 × 10 18 cm −2 ( E > 1 MeV) at the irradiation temperature 12 K. It decreases from 19.5 to 18.8 K. It is established that significant degradation of T c takes place as a result of subsequent long-duration annealing at 300 K with simultaneous increase of the superconducting transition width. This indicates the appearance of inhomogeneities in the matrix in the form of disordered or nonstoichiometric clusters.