Oxidation by Fenton like reactions (Fe³⁺/H₂O₂) is economically process for destructive hazardous pollutants in waste water. The effects of different parameters such as, amaranth red dye, ferric chloride, hydrogen peroxide concentrations, pH value of solution, temperature and the presence of inorganic ions (carbonate, nitrate, chloride) on oxidative decolorization of amaranth were investigated. Amaranth degradation by (Fe³⁺/H₂O₂) reagent was found to follow first order kinetic model. Under optimum condition, pH = 2.6 and [FeCl₃] = 3.75 × 10^-4 mol·dm^-3, the amaranth in aqueous solution with an initial concentration of 5 × 10^-5 mol·dm^-3 was degraded by 95% within 6 minutes. Increasing temperature in the range of 298 - 308 K increases the rate of dye degradation. Thermodynamic constants, ΔH*, ΔS* and ΔG* were evaluated. The results implied that the oxidation process was favorable and endothermic.