Spectrophotometric determination of mercury (II) is carried out with 8-hydroxy-quinoline as a complexing reagent in aqueous phase using cationic surfactant cetylpyridinium chloride (CPC). Beer’s law is obeyed over the concentration range 0.5-4.0 mg m1. The lmax molar absorption molar absorptivity and sandell’s sensitivity were 400 nm; emax = 0.75 x 104 mol-1dm3.cm-1 is 0.65 and (30.9) ng cm-2. Validation of this method has been made by comparing the results with those obtained by Atomic Absorption Spectroscopy (AAS) No significant difference was observed in the result obtained by the two methods at 95% confidence level. The method is simple, accurate, economical and can be applied for the determination of mercury (II) in industrial wastewater samples.