The crystal structure of the title compound, [Na(C(3)H(3)N(2)S(3))(H(2)O)(2)](n), features polymeric chains made up of O⋯O edge-shared NaSN(H(2)O)(4) units running along the b axis. The Na(+) ion and all non-H atoms of the thia-diazole ligand lie on a mirror plane.