This paper reports the extraction of the ion-pair formed by the tetrabutylammonium cation and the copper complex with thiocyanate from aqueous to MIBK solutions. The variables which affect the extraction efficiency were investigated and the optimal conditions for the efficiency to be almost 100 per cent were determined. The extraction can be accomplished between pH 1 and 7 and an excess of ammonium thiocyanate and tetrabutylammonium chloride is necessary. The absorption spectrum of the ion-pair in MIBK has a maximum at 510 nm. At 510 nm the absorbance is proportional to the concentration of copper in solution. Thus, the spectrophotometric determination of copper is possible, after the extraction by MIBK. Beer's Law is verified for a range between 3.8 × 10−5and 7.6 × 10−4M. after interferences were investigated, the precision and accuracy of this method were checked by determining the copper content in an alloy whose composition was certified by British Chemical Standards.