The study was primarily focused on novel, simple and environmentally benign technique for the synthesis of copper nanoparticles (CuNPs) and comparing the catalytic activity in CuNPs/Peroxodisulfate (PDS) and CuNPs/Peroxomonosulfate (PMS) process for degradation of Methyl Orange (MO). Green synthesized CuNPs were characterized by different instrumental techniques and results indicate synthesized NPs are in crystalline nature and cubical shape with 48 nm size. The increasing concentration of nanocatalyst, peroxosulfates, Dye, initial pH and high temperature rapidly promoted the degradation kinetics of MO. The degradation of MO in CuNPs/Peroxosulfates system is modeled as pseudo-first order kinetics and activation parameters were also determined. The maximum degradation efficiency of MO reached 92% in 60 min for CuNPs/PDS system and 98% in 30 min for CuNPs/PMS system at optimum reaction condition. Sulfate radicals (SRs) (SO4−) were identified as oxidative species using specific alcohols. Furthermore, LC–MS analysis and results of UV–vis spectral changes were used to determine the structure of intermediates arising from MO by CuNPs/Peroxosulfates degradation. The degradation products revealed that the degradation mechanism proceeds through an oxidative cleavage of the azo linkage in the formation of SO3− and NO3− as end products. Employing CuNPs to enhance oxidation capacity of peroxosulfates for degradation of MO is a novel, efficient, promising and environmental-friendly method since it does not require costly reagents.