Sodium hydroxide-modified graphene oxide was used as manganese oxides support for the preparation of nanocomposites via a one-pot preparation route for the degradation of Reactive Black 5. The nanocomposites were characterized for their structure by X-ray diffraction, for their textural properties by Nitrogen adsorption, and for their surface chemistry by Fourier transform infrared spectroscopy, potentiometric titration, and thermal analysis measurements. The nanocomposites prepared showed to possess high activity for the degradation/oxidation of Reactive Black 5 at ambient conditions, without light irradiation, which was higher than that of the precursors manganese oxides and can be attributed to the synergistic effect of the manganese oxides and the modified graphene oxide.