In this study, a surface modification of the poly (ethylene terephthalate) (PET) film using TiO2 photocatalytic treatment was investigated. In order to enhance the adhesion strength between the PET film and the electroless copper film, the effects of TiO2 crystal forms, TiO2 particle sizes, and TiO2 content, as well as treatment condition, upon the surface contact angle, surface characterization, and adhesion strength were investigated. Anatase TiO2 with a particle size of 5nm had a high catalytic activity and dispersibility in aqueous solution. After the optimal photocatalytic treatment, the surface contact angle of the PET film decreased from 84.4 degrees to 19.8 degrees, and the surface roughness of the PET film increased from 36 to 117nm. The adhesion strength between the PET film and the electroless copper film reached 0.89 KN m(-1). X-ray photoelectron spectroscopy analyses indicated the carbonyl group was formed on the PET surface after photocatalytic treatment, and the surface hydrophilicity was improved. Consequently, TiO2 photocatalytic treatment is an environmentally friendly and effective method for the surface modification of the PET film.