Measurement of the extraction equilibrium of silver(I) from nitric acid and aqueous ammonium nitrate solutions with triisobutylphosphine sulfide (TBPS) in toluene was carried out at 303 K to examine the effects of the concentrations of nitrate and hydrogen ions and silver in the aqueous phase as well as that of the extractant. It was found that the extraction equilibrium is explained in terms of the solvation of silver(I) by TBPS with simultaneous transfer of a nitrate ion into the organic phase to form an ion-pair and that the extracted species in the organic phase is the sliver: TBPS 1:2 complex.