In the present study, effect of pre-oxidized (PO) CuO layer in the joining between polyethylene terephalate (PET) and copper (Cu) by using pulsed Nd:YAG laser was investigated. The experimental result for PET/PO Cu (with pre-oxidized layer) and PET/Cu (without pre-oxidized layer) were presented in this paper. The results showed the pre-oxidation surface improved the welding efficiency. The welded area and tensile shear failure load (TSFL) of PET/PO Cu joint were increased when pre-oxidized layer was introduced. This indicates that high heat was absorbed during laser irradiation of PET/PO-Cu joint compare to PET/Cu joint. On the other hand, the fracture surface of PET/PO-Cu showed the presence of Cu and Cu oxide particles in the PET side. While in case of PET/Cu, no occurrence of Cu particles can be observed. The presence of Cu oxide particles and Cu particles were believed may increase PET/PO Cu joint shear force. From the cross-sectional observation of PET/PO Cu joint interface, it was found that an oxide layer in the laser irradiation area was removed and PET seemed to have intimate contact with Cu surface.