We report the results of calculations which were performed to investigate the equilibrium structures and electronic and magnetic properties of small BnNi(n≤5) clusters within the framework of density functional theory. We obtained the structures of BnNi(n≤5) clusters at different spin multiplicities and determined the lowest-energy structures of BnNi(n≤5) clusters. The results show that the spin multiplicities of the lowest-energy clusters are 2, 1, 2, 1 and 2, respectively. We also studied the magnetic properties of the lowest-energy clusters systematically and found that both the magnetic moment of Ni atom and the total magnetic moment of clusters oscillate with increasing size.