A new gold(I) complex with N-acetyl-L-cysteine was synthesized and characterized by chemical and spectroscopic techniques. The elemental and thermal analyses of the solid compound fit to the composition AuC₅H₈NO₃S · 0.75H₂O. Solid-state ¹³C-nuclear magnetic resonance (SSNMR) and infrared (IR) analyses indicate the coordination of the ligand to Au(I) through sulfur. The insolubility of the complex in both polar and non-polar solvents supports a polymeric structure. The antibacterial activity of the complex was evaluated by antibiogram assays using the disc diffusion method. The compound showed effective antibacterial activity against Staphylococcus aureus (Gram positive) and Escherichia coli (Gram negative) bacterial cells.