A series of manganese oxide-loaded SBA-15 (MnSBA-xh, x = 1, 2, 3, 4, 5, 6, h hour(s)) mesoporous materials are synthesized via a facile, in-situ reduction method with a surfactant template. The composite materials are characterized using Fourier-transform infrared spectroscopy, X-ray diffraction, N-2 sorption isotherms, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy energy-dispersive spectroscopy, and CO oxidation catalysis. The results show that a high content of manganese (an atomic ratio of Mn/Si from 0.12 up to approximately 1) could be loaded into the channels of SBA-15 when treated with an aqueous solution of potassium permanganate, while retaining the ordered mesostructure and large surface area of SBA-15. Increasing the manganese oxide content results in a gradual decrease in the specific surface area, pore size, and pore volume XPS spectra are employed to confirm the redox reaction between KMnO4 and the surfactant. CO-conversion tests on the calcined MnSBA-2h sample (MnSBA-2h-cal) shows that it has a repeatable, and relatively high, catalytic activity.