abstract: The efficiency of UV/Fenton process was investigated to treat the paper recycling industry wastewater. The effect of Fenton treatment on various water quality parameters namely, chemical oxygen demand (COD), biological oxygen demand (BOD), pH, electrical conductivity (EC), total suspended solids (TSS), total dissolved solids (TDS), total solids (TS), nitrates, phosphates, and heavy metals (Hg, Pb, Cd, Cr, Cu) was investigated. The COD, BOD, EC, TDS, TSS, TS, nitrates, phosphates, and heavy metals reduction percentages remained very high (>90%) for various wastewater samples treated. The strategy involving gradual increase in the mass loading (in terms of increasing the share of original wastewater in dilution showed that the UV/Fenton process was efficient to treat paper industry wastewater. The best results were obtained when paper industry wastewater was diluted with nine parts as real wastewater and one part dilution by freshwater. The findings of this study demonstrate that the UV/Fenton process can significantly break down a variety of pollutants from paper recycling industry wastewater.