The influence of fast neutron irradiation on critical current Ic, mechanical properties and the strain dependence of Icfor a bronze processed fine multifilamentary Nb3Sn superconducting composite has been investigated. The neutron irradiation has been performed in a fission reactor at the reactor ambient temperature (<355 K) up to a neutron fluence of 3.6×1019n/cm2(En>0.1 MeV). The effect of annealing after irradiation has also been investigated. It has been found that the composite grows harder and more brittle with irradiation. The strain which gives the maximum Icin Icvs. strain relation is increased with irradiation. The reversibility of strain induced change in Icis degraded by irradiation. Annealing at 723 K and 973 K (2 hr) after 3.6×1019n/cm2irradiation recovered successively the mechanical properties and strain dependence of Icup to the levels before irradiation.