Graphene/cobalt manganese oxides nanocomposites were prepared from their precursor through chemical reduction where NaOH was used as a reducing agent. The obtained GNs/Co-Mn nanocomposites were used as photocatalyst for the photodegradation of Neutral Red Chloride (NRC) dye in aqueous solution under sunlight as a function of time and catalyst dosage. The morphology and photodegradation study was carried out using scanning electron microscopy (SEM) and UV-VIS spectrophotometry, respectively. The SEM image showed the presence of Co-Mn nanoparticles on the surface of GNs, which were also confirmed by energy dispersive X-ray analysis. The photodegradation study of NRC showed that the degradation of dye increased with an increase in irradiation time, and 94% of dye was degraded within 5 min by GNs/Co-Mn. Photodegradation was also carried out with recovered catalyst, which degraded about 90% of dye within 5 min. The effect of catalyst dosage on the degradation of dye was also studied.