In the crystal of the title compound, C(12)H(8)N(2)O(4)S, mol-ecules are linked into chains by a series of inter-molecular O-H⋯O, N-H⋯O and N-H⋯N hydrogen bonds. The ninhydrin and amino-thia-zolidine units make a dihedral angle of 66.41 (3)°. The crystal structure indicates the presence of equimolar R and S enanti-omers in the crystal lattice, due to the presence of a chiral centre in the title compound.