The TmCo 3 compound crystallizes in the rhombohedral PuNi 3-type structure. TmCo 3 exhibits a kink in the resistivity and AC susceptibility near the spin-reorientation temperature ( TSR≅17 K). The spin-reorientation transition observed in TmCo 3 is ascribed to the competition between the anisotropies of Co and Tm atoms. The value of spontaneous magnetization is equal to 3.1 μB/f.u. and is closer to the value 3.31 μB/f.u. obtained by ab initio calculations, which show that the moments on Co atoms depend on their local environments.