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Application of oxygen releasing compounds (ORCs) is considered as a novel method in petroleum hydrocarbon remediation from groundwater. ORCs destroy chemically the contaminant by exposure to water which results in hydroxyl radical generation or biologically remove the pollution by biostimulation of the groundwater native microorganisms aerobically. In the present study, calcium peroxide (CaO₂) nanoparticles were applied to supply the required oxygen for growth and activity of the native microorganisms to consume naphthalene (20 ppm) as a carbon source. Additionally, the effect of CaO₂ content, temperature and pH on the performance of nanoparticles were investigated in the naphthalene removal. The results indicated that the microbial population was sharply increased in the presence of 400 mg/L of nanoparticles and at 30^oC and the contaminant was completely removed after 20 days at neutral pH. Furthermore, naphthalene was 100% remediated from groundwater at pH 3, 7.4 and 12 after 2, 20 and 30 days, respectively. This proved the acceleration of chemical oxidation under the acidic condition. At 15 and 30 ± 0.5 ^oC the contaminant was removed from the media within 15 and 20 days respectively. Meanwhile, only 75% of contaminant was remediated from groundwater within 30 days at 4 ±0.5^oC which was due to the reduction in the biological activity and the chemical reaction rate.