Mn-CdS nanoflowers were successfully deposited using hydrothermal technique at 150 degrees C for 2 h. The effect of changing the dopant concentration on the structural, morphological and optical properties of the produced samples was investigated. The XRD diffraction technique showed the formation of hexagonal and cubic phases, whereas the FE-SEM analysis confirmed the success of the formation of flower-like nanostructures. The UV-Visible spectra revealed that the energy band-gap values decreased with increasing manganese concentrations. The optical band-gap ranges were 2.4, 2.35, 2.25, 2.14 and 1.76 eV thin films with concentrations of (0%, 1%, 2%, 3% and 4%) for undoped and Mn-doped cadmium sulfide. The results of UV-Vis spectroscopy agree with the conclusions of the PL study. The surface morphology was studied using scanning electron microscopy and atomic force microscopy. According to the results, the crystalline size decreased as doping concentrations increased. The Mn-doped cadmium sulfide films exhibited unprecedented photocatalytic activity for the decomposition of methyl blue (MB) and methyl violet (MV) dyes, due to high surface area, low energy gap and efficient charge separation properties for the prepared films. [GRAPHICS] .