Pure and metal (Cu, Mn) doped In2S3 nanoparticles were prepared by the standard co-precipitation technique. This work aims to study the influence of metal (Cu, Mn) on the synthesized nanoparticles' structural, morphological, optical, photoluminescence, and electrical properties (NPs). The XRD pattern reveals that the metal (Cu, Mn) doped In2S3 NPs were polycrystalline with a cubic phase whose particle size varies between 36.2 and 49 nm. A significant decrease in the crystallite size was observed after metal doping. It is noted from the EDS spectra the elements like In, Cu, Mn and S are present in the NPs. The optical studies reveal that the high transmittance (80%) was observed for pure In2S3 NPs makes them an efficient window layer for solar cell applications. Also, the calculated bandgap energy was found to increase ( 2.8 – 3.28 e V) for metal doping. Photoluminescence measurements reveal that the photoemission is mainly due to the donor-acceptor pair transitions. The electrical studies indicate that the electrical conductivity decreases significantly with doping, and maximum electrical conductivity of 1.28 x 10-6 (Ω m)-1 was obtained for pure In2S3 NPs. A photocatalytic study reveals that high photocatalytic activity is observed for Mn-doped NPs under Methylene blue (84%).