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Rational design of noble metal promoted oxide-sulfide p-n heterojunctions with improved photon harvesting ability and opto-electronic features is an innovative approach for achieving targeted photoreduction reactions. In this study, a one pot hydrothermal synthesis route is developed for fabrication of CuS/Fe2O3p-n heterostructure and subsequently used as host matrix for photo-deposition of Pd (2 wt%) nanodots. The Pd/CuS/Fe2O3encompasses distinct morphological features including rhombohedral Fe2O3, nanodisc shaped CuS and Pd nanodots interwoven among each other to form the ternary composite. The compatible low band gap energies of Fe2O3and CuS, constructive band positioning, plasmonic nature of Pd and formation of microscopic p-n heterojunction led to efficient visible light harvesting and improved photo-electrochemical properties. The photoredox feature of the ternary heterostructure material is successfully exploited for reduction of heavy metal (Cr6+, k = 0.062 min−1), structurally diverse nitroarenes (70–93 %) and photocatalytic green H2evolution (1120 μmolh−1g−1). Mechanistic investigation revealed a synergistic S-scheme charge channelization pathway between CuS and Fe2O3components whereas the plasmonic Pd nanodots act as a co-catalyst in improving the light absorption property and photocatalytic activity of the ternary heterostructure. The superior photoreduction activity of the Pd/CuS/Fe2O3composite has been ascribed to the combined effect of p-n heterojunction formation, highly negative conduction band potential of CuS (−0.54 eV) and the ability of Pd nanodots to act as electron sink for rapid electron transfer to the reactant species. This study provides a new outlook towards facile fabrication of metal promoted p-n heterojunctions for potential applications in selective photocatalytic reduction reactions.