The title compound, [Tl(C2H6OS)6](NO3)3, consists of six dimethyl sulfoxide (DMSO) molecules coordinated to a TlIII atom, which lies on a 3 axis, and three nitrate anions (3. symmetry) to neutralize the charge. The coordination polyhedron around the TlIII atom is octahedral, defined by six O atoms of the DMSO molecules. In the crystal structure, C— H O hydrogen bonds are observed. One of the nitrate groups exhibits half-occupation.