Surface water contamination by dye pollutants is a global environmental concern. The treatment of effluent from textile waste using metal oxide-based photocatalysts is a widely employed approach owing to its efficacy and simplicity. Herein, the synthesis and fabrication of novel visible radiation receptive manganese oxide and mesoporous silica nanocomposites (Mn2O3/SiO2) is described. Surface morphology of nanocomposites using scanning electron microscopy (SEM) displayed spherical shaped agglomerated structure. The chemical composition of nanocomposites was examined by using energy dispersive x-ray (EDX) analysis respectively indicating the presence of respective elements. Structural analysis was carried out by using XRD spectroscopy, while optical properties were evaluated by employing UV-visible spectroscopy. The photocatalytic activity of pure Mn2O3 and SiO2 nanoparticles as well as their nanocomposites with two different ratios Mn2O3/SiO2 (1:3) and Mn2O3/SiO2 (3:1) were evaluated by using methyl orange (MO) as a model dye. The band gap energy of Mn2O3/SiO2 (1:3) and Mn2O3/SiO2 (3:1) nanocomposite was 2.39 eV and 1.69 eV respectively. The nanocomposites exhibited improved photocatalytic efficiency as compared to pure nanoparticles as a function of pH and mixing ratio. For instance, at pH 7.0, Mn2O3/SiO2 (1:3) nanocomposite has depicted maximum degradation efficiency of 68% for degradation of MO as compared to Mn3O4/SiO2 (3:1) nanocomposite, Mn3O4 and SiO2 nanoparticles. However, at pH 2.0 Mn2O3/SiO2 (3:1) nanocomposite had shown maximum degradation efficiency of 99% as compared to Mn2O3/SiO2 (1:3), Mn2O3 and SiO2 nanoparticles. The degradation reaction followed pseudo first order kinetics. At pH 7.0, the rate constant values of nanocomposites i.e. Mn2O3/SiO2(1:3) and Mn2O3/SiO2(3:1) comes out to be 4.68 × 10-3 min-1 and 2.49 × 10-3 min-1 respectively. At pH 2.0, the rate constant values calculated for Mn2O3/SiO2(1:3) nanocomposite and Mn2O3/SiO2(3:1) nanocomposite was 4.91 × 10-3 min-1 and 1.24× 10-2 min-1 respectively. The easy fabrication of these nanocomposites coupled with facile tuning of their properties make them suitable contenders for efficient dye degradation in wastewater treatment.