Abstract: A potentiometric study is conducted of equilibria of the formation of silver(I) complexes with thiourea and N-phenylthiourea (L) using a silver electrode in the 278.16–318.16 K range of temperatures at an ionic strength of I = 0.11 M (0.1 NaNO3 + 0.01 HNO3). It is found that mono- and binuclear complexes are present in the studied systems in a wide range of concentrations of Ag+ ions (1 × 10−5–1 × 10−3) in solution at different temperatures, and the Ag2L32+ form dominates in both systems. It is shown that the stability of mono- and binuclear complexes falls as the temperature rises. Thermodynamic parameters (ΔH°, ΔG°, and ΔS°) are determined for mononuclear complexes. © 2022, Pleiades Publishing, Ltd.