The title complex, [AuCl(C18H16N5S)]Cl·1.5H2O, may be considered as a gold(I) compound with the corresponding metal site coordinated by a thio-semicarbazone ligand through the S atom. The ligand adopts an E conformation and the gold(I) atom displays the expected linear geometry with a Cl atom also bonded to the metal ion [Cl-Au-S = 174.23 (5)°]. One of the pyridyl rings is protonated, giving the gold complex an overall positive charge. Two solvent water mol-ecules, one of which is located on a twofold rotation axis, and a non-coordinating chloride ion complete the structural assembly. The mol-ecular structure is stabilized by intra-molecular and inter-molecular N-H⋯Cl, N-H⋯N, O-H⋯Cl and O-H⋯O hydrogen bonding.