A simple and accurate spectrophotometric method for determination of trace amounts of Cu 2+ ions in various real samples has been described. The spectrophotometric determination of trace amount of Cu 2+ ion using diacetyl monooxime (DAMO) in the presence of cetyltrimethylammonium bromide (CTAB) as cationic surfactant has been carried out. The Beer's law is obeyed over the concentration range of 0.1-22.0 µgmL-1 of Cu 2+ ion with the detection limits of 1.3 ngmL-1. The influence of type and amount of surfactant, pH, complexation time and amount of ligand on sensitivity of method were optimized. Finally the repeatability, accuracy and the effect of interfering ions on the determination of Cu 2+ ion were evaluated.