1-(3-amino-4-thia-1,2-diazaspiro[4.11]hexadec-2-en-1-yl)ethan-1-one was synthesized and experimentally characterized by using FT-IR, H-1 NMR, C-13 NMR, and UV-Vis spectroscopy. The structure of the compound was confirmed by single-crystal X-ray diffraction. In the crystal structure, the molecules are linked by pairs of N-HN hydrogen bonds, forming centrosymmetric dimers with theclose=")">8 graph-set motif. The water molecule also plays an important role in the stabilization of the crystal structure, bridging the dimers to form a two-dimensional supramolecular network. The molecular geometry, frontier molecular orbitals, vibrational frequencies, electronic properties, and molecular electrostatic potential were calculated using density functional theory (DFT) with the B3LYP/6-311G(d,p) basis set. Geometric parameters, vibrational assignments, and electronic properties such as calculated energies, excitation energies, and oscillator strengths were compared with the experimental data, and it was seen that the theoretical results support the experimental parameters.