This study provides a comprehensive database of sulfur isotope values from Greece, including samples of C3 and C4 plants and terrestrial and aquatic animal bones. This comprehensive analytical approach examines sulfur isotopes—along with carbon and nitrogen—in modern plants, terrestrial mammals, and fish bones (fresh and marine reservoirs) from Greece. The results show a clear offset in δ34S values between terrestrial and aquatic animals, influenced by their dietary sources from marine or freshwater environments. This δ34S offset and the clear difference between S-C-N isotopes permits the reconstruction of the dietary habits of domesticated herbivores and demonstrates differences in husbandry practices and animal movements. Additionally, the combination of sulfur and nitrogen values allows the reconstruction of the diet of omnivores, revealing the type of protein consumed. Finally, this isotopic dataset will provide an essential backbone for future archaeological, ecological, and forensic studies.