Oil pollution has been identified as the major contribution to the deterioration of water and soil quality, even in low concentrations. Due to development of petrochemical, oil and gas industrial, large amount of oil pollutant had been released into the water and wastewater. There are various physical, chemical, biological and thermal methods has been used for remediation of oil contaminated water and wastewater. In this regards, Microwave (MW) irradiation as a thermal methods, recently has been widely used to remediate water and soil contaminated with organic pollutants (e.g. petroleum hydrocarbons), because of its high efficiency, short remediation time and high heating rate. So this study aimed to evaluate effects of microwave radiation on remediation of oil contaminated water and wastewaters. Crude oil was used as the model pollutant using sodium dodecyl sulphate (C 12 H 25 NaO 4 S) emulsifier to generating the initial oil-water emulsion. In order to achieve high removal efficiency of petroleum hydrocarbon, optimum level of irradiation time (min), MW intensity (watt), initial concentration of pollutant (%) and H 2 O 2 concentration (mg/L) were determined and then different aqueous solutions (Distilled water, Isfahan drinking water and Tehran Refinery's wastewater) were irradiated under optimum conditions. Measurements were conducted in different parameters such as temperature, pH, removal of Chemical Oxygen Demand (COD) and removal of Total Petroleum Hydrocarbons (TPH). Each state of laboratory processes repeat in three times and the experimental data collected was analyzed by performing the analysis of variance (ANOVA) with Tukey comparison test (?=5%) using the Minitab 17 Software. As a first step, crude oil-water emulsion (10 mg/L) was treated under various MW irradiation time (2.5, 5, 7.5, 10, 12.5 and 15 min) with medium MW intensity of 600 watt and efficient time was evaluated. In the second part, the effect of MW intensity (300, 450, 600 and 850 watt) on the removal efficiency was studied. Besides, initial concentration of TPH (0.25, 0.5, 0.75 and 1%) and H 2 O 2 concentration (500, 1000 and 1500 mg/L) were individually studied. Finally, the effect of MW radiation on TPH removal was investigated in different aqueous solution considering the optimized conditions obtained from previous experiments. Results indicated that 10 min MW irradiation (with 26.6% of COD removal and 54.5% TPH removal) was the most efficient radiation time and the most removal of COD and TPH occurred in MW irradiation intensity of 850 watt (37.4% and 63.2%, respectively). According to results, initial concentration of 1% had sufficient effect on COD and TPH removal (35.9% and 64.3%) and adding H 2 O 2 with initial concentration of 1000 mg/L has significant effect on removal efficiency of pollutant (with 51.4% of COD and 79.8% of TPH removal). The result of MW radiation in optimized condition on different aqueous solution showed that wastewater had the maximum removal of COD and TPH (50.7% and 66.0% respectively). In addition, biodegradability (BOD 5 /COD) of wastewater solution was increased from 0.4 to 0.7 after using optimized condition of MW radiation. Overall, it can be concluded that MW radiation/H 2 O 2 in efficient condition is a suitable method for removal of petroleum hydrocarbons from water and wastewater solutions and more researches to enhance TPH removal efficiency in MW/H 2 O 2 method, specially using sorbents are recomended. Key words: Water and Wastewater, Microwave Radiation, TPH Remediation Efficiency, Total Petroleum Hydrocarbon (TPH), Crude Oil .