Irradiation-induced precipitation in Ni-Sn binary alloys was examined by positron annihilation coincidence Doppler broadening (CDB) and lifetime measurements, and the correlation between precipitation and void growth was studied. S-W plots obtained from CDB measurements of pure Ni and Ni-Sn alloys were compared. The change in S-W plots in Ni-0.05at.%Sn with increasing neutron dose was nearly the same as that of pure Ni, while that of Ni-0.3at.%Sn and Ni-2at.%Sn deviated from that of pure Ni. Precipitation of Ni3Sn was detected after annealing of Ni-2at.%Sn, and the precipitation was promoted by irradiation. In Ni-0.3at.%Sn, no precipitation was detected after an 1173 K heat treatment, but irradiation-induced precipitation did occur. The precipitation and the frequency of one-dimensional motion of interstitial clusters were closely correlated, and the clusters and vacancies annihilated each other. The precipitation suppressed void growth.