The hydrodechlorination (HDC) of transformer oil, which consists of a mixture of chlorinated benzene compounds (ClBzs) and polychlorinated biphenyls (PCBs), was carried out in liquid phase by using Pd/C, Ru/C, Rh/C, and Pd/Al2O3 catalysts under mild reaction conditions: 25C and hydrogen pressure of 2 bar. On the Pd/Al2O3 catalysts, the total hydrodechlorination of the ClBzs and PCBs was reached after 50h of reaction. Benzene and biphenyl aromatic compounds as well as total and partially hydrogenated products such as cyclohexane, bicyclohexane, and cyclohexylbenzene were obtained.