In the mol-ecule of the title compound, C(12)H(6)N(2)O(3)S, the central heterocyclic ring is oriented at dihedral angles of 3.25 (6) and 2.28 (7)° with respect to the benzene and pyridine rings, respectively. The dihedral angle between the benzene and pyridine rings is 5.53 (7)°. In the crystal structure, inter-molecular C-H⋯O hydrogen bonds link the mol-ecules into chains.