The title compound, C9H10N4OS0.5H2O, crystallizes with two independent molecules (A and B) in the asymmetric unit, together with a water molecule of crystallization. The acetamide moiety, which has an extended conformation, is inclined to the pyridine ring by 7.95 (16) in molecule A and by 1.77 (16) in molecule B. In the crystal, the A and B molecules are linked by two N—H  Ocarbonyl hydrogen bonds, forming a dimer. The dimers are linked via N—H  N hydrogen bonds, forming ribbons that are linked by N—H  Owater hydrogen bonds to form sheets parallel to (110). The sheets are linked by O—H  N hydrogen bonds,
forming slabs, and between the slabs there are weak slipped parallel – interactions [inter-centroid distance =
3.734 (2) A ° , interplanar distance = 3.3505 (11) A ° and slippage = 1.648 A ° ], forming a three-dimensional structure