Response surface methodology (RSM) was employed to optimize nitrogen, phosphorus and inocula concentrations for the co-metabolic degradation of chlorinated aromatic hydrocarbons (CAHs) and benzene, toluene, ethylbenzene and three isomers of xylene collectively known as BTEX using an indigenous aerobic microbial isolate from contaminated soil in lab-scale. The interactive effects of the three variables toward the bioremoval of BTEX (600 mg/kg), cis-dichloroethene (cis-DCE 10 mg/kg) and trichloroethene (TCE 10 mg/kg) were evaluated in a central composite design (CCD) with varying concentrations (nitrogen 40-200 mg/kg; phosphorus 4-36 mg/kg; inocula volume 1-9 mL, with the incubation period of 72 h at 25°C and 150 rpm). On the basis of the response surface and contour plots after 6 days of incubation, the optimal C:N:P ratio and inocula concentration for BTEX and CAHs degradation were obtained, which would help enhance the applicability of bioaugmentation technology to the mixed wastes contaminated sites.