Total energy calculations of a neutral and charged Ni-5 cluster and its isomers corresponding to different spin multiplicities have been carried out using density functional theory and generalized gradient approximation. It is demonstrated that its magnetic moment can be determined by comparing theoretical results with photo-detachment spectroscopy experiment. We find Ni-5 to have two nearly degenerate isomers with magnetic moments of 0.8 mu (B) per atom and 1.2 mu (B) per atom.