The complex of silver (I) with the reagent 3-methyl-1, 2-cyclopentanodione dithiosemicarbazone, 3-Me-CPDT, has been studied spectrophotometrically. Few properties of the complex such as its composition, stability, and free energy of formation have been determined. A sensitive method of analysis for silver in aqueous solutions has been developed based on the spectrophotometric measurement of the absorption of the Ag-3-Me-CPDT complex. The optimum conditions for applying this method for the determination of Ag(I) have been determined. These conditions include the standing time, pH, wavelength, and the effect of interfering ions.