A new and improved synthetic route to WSF4 was developed from the reaction of WF6 and Sb2S3 in anhydrous HF. Tungsten sulfide tetrafluoride was characterized by Raman and F-19 NMR spectroscopy for the first time in HF solvent. Both studies provided evidence for its monomeric form in HF solution. In the solid state, WSF4 was also characterized by Raman and infrared spectroscopy. The WSF4 center dot CH3CN adduct was prepared from WSF4 and CH3CN in anhydrous HF solvent and by the direct combination of WSF4 with excess CH3CN, and was characterized by Raman and infrared spectroscopy in the solid state and F-19 NMR spectroscopy in CH3CN solution. The crystal structure of WSF4 center dot CH3CN was obtained and showed that CH3CN coordinates to W in an end-on fashion and trans to the W-S bond. Quantum-chemical calculations using B3LYP and PBE1PBE methods were used to calculate the gas-phase geometries and vibrational frequencies of WSF4 and WSF4 center dot CH3CN.