The new acesulfamate salt, TlC4H4NO4S, was prepared by reaction of acesulfamic acid and thallium(I) carbonate in aqueous solution. Its crystal and molecular structure was determined by single crystal X-ray diffraction methods. The substance crystallizes in the monoclinic space group P21/a, with unit cell parameters a = 7.5844(4) Å, b = 9.7268(5) Å, c = 10.8105(5) Å, β = 105.174(6)°, and Z = 4 molecules per unit cell, and is isostructural with the corresponding sodium, potassium, rubidium and cesium salts. The FTIR and Raman spectra of the compound are also recorded and briefly discussed.