Synthesis of metal chalcogenides nanostructures is of profound importance in obtaining desired properties for photo-sensing device fabrication. The present proposed work concentrates on the effect of oleic acid in the preparation of NiS and SnS/NiS composites, and their photodiode properties were examined. Synthesized NiS and SnS/NiS nanosystem characterized by XRD analysis, Raman analysis, Field Emission Scanning Electron Microscopy micrographs. Hexagonal structure of NiS and hexagonal and orthorhombic composite structures SnS/NiS composite was confirmed with XRD patterns. The single-phase SnS nanoparticle and SnS/NiS nanocomposite were confirmed with Raman analysis. The change in morphology while increasing oleic acid on the preparation of NiS and SnS/NiS as aggregated quasi sphere structures were verified with FE-SEM micrographs. SnS/NiS fabricated with different ratios, and oleic acid-assisted NiS composite particles show better photo-response, which is essential for photodiode application.