Surface roughness of acrylonitrile-butadiene-styrene (ABS) resin prior to metallization is treated generally with sulphuric/chromic acid system. However, the presence of chrominum (VI) ion imposes serious environmental problems. In this work, TiO2 photocatalytic treatment was used to enhance the adhesion strength between the ABS surface and the electroless copper film. Effects of the TiO2 content, irradiation time and UV power upon the surface topography, surface characterization and the adhesion strength were investigated. The results indicated that the surface hydrophilicity of ABS resin and the adhesion strength between the electroless copper film and ABS surface increased with an increase in the UV power and a prolongation in irradiation time, and did not increase linearly with an increase of TiO2 content. Though the surface topography of ABS changed little, the adhesion strength reached 1.25kN/m, which was higher than that in the optimal H2SO4-MnO2 colloid. The surface chemistry results indicated that -COOH and -OH groups formed with the photocatalytic treatment and the absorption strengths increased with the UV power. XPS analysis results further demonstrated that the contents of C=O and -COOH reached 6.4 and 4.9% with the photocatalytic treatment, which was much higher than that of the H2SO4-MnO2 colloid (3.9 and 3.1%). The high contents of C=O and -COOH groups enhanced the surface hydrophilicity of the ABS resin and improved the adhesion strength between the electroless copper film and ABS resin. The results indicated that the photocatalytic treatment was an environment-friendly and effective method to replace the commercial wet chemical process for ABS surface modification.