A series of Mn₃Co₁₆O_x composite oxides catalysts were fabricated via a solid-phase synthesis using different manganese precursors (namely manganese acetate (A), nitrate (N), and sulfate (S)). It has been demonstrated that the obtained catalysts presented variable catalytic activities for CO oxidation and remarkable diversity of physicochemical properties closely depending on the manganese precursors. In detail, the catalytic activity and catalytic durability for CO oxidation under humid conditions generally followed a descending order of Mn₃Co₁₆O_x-A > Mn₃Co₁₆O_x-N > Mn₃Co₁₆O_x-S. The optimum catalytic performance of Mn₃Co₁₆O_x-A was predominantly attributed to its larger specific surface area, significantly higher low-temperature reducibility and lattice oxygen mobility, and more plentiful oxygen vacancies.