Nanorods and nanosheets of new cobalt hydroxide carbonates have been fabricated through hydrothermal method using CoCl 2·6H 2O and CO(NH 2) 2 in the presence of polyvinylpyrrolidone (PVP). The products were characterized using Fourier transform infrared spectroscopy, elemental analysis, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy and transmission electron microscope/selected area electron diffraction. The nanorods and nanosheets crystallize in different crystal structures with the chemical formula of Co(OH) 0.44(CO 3) 0.78·0.29H 2O and Co 2(OH) 2CO 3, respectively. For the hexagonal phase with the morphology of nanorods, its lattice parameters are: a = 10.335(5) Å, c = 3.124(1) Å, the possible space group is P622(177), and the number of chemical formula per unit cell is Z = 3. For the monoclinic phase with the morphology of nanosheets, its lattice parameters are: a = 9.362(1) Å, b = 12.175(5) Å, c = 3.281(4) Å, β = 91.879(2), the possible space group is P21/ a (14), and the number of chemical formula per unit cell is Z = 4. Our results indicate that the morphology and crystal structure of cobalt hydroxide carbonates are controlled by the reaction temperature, reaction time and PVP.