A facile, cost-effective, template-free chemical method was developed for the synthesis of β-Co(OH)2 nanoplatelets under the different preparation conditions. The morphology and microstructure of as-synthesized samples were examined by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS), respectively. The observations revealed the formation of a single phase of the hexagonal brucite-like β-Co(OH)2, which had an irregular hexagonal disk with angles of adjacent edges of 120°, edge lengths ranging from 200 to 300nm, and thicknesses of 20–40nm. When investigated as catalyst for CO oxidation, the β-Co(OH)2 nanoplatelets exhibited good catalytic activity for CO. Among β-Co(OH)2 nanoplatelets, the sample prepared at 100°C for 8h performed the best, giving the T100% (the temperature required for achieving a CO of 100%) of 120°C for the oxidation of CO. There are good correlations of Co3+/Co2+, the absorbed Ox− ions and surface OH group with catalytic activity of the samples for CO oxidation.