The title compound represents the thallium(I) salt of a substituted 1,2,5-oxadiazole, [Tl(C3H3N4O3)]
n
, with amino- and hydroxamate groups in the 4- and 3- positions of the oxadiazole ring, respectively. In the crystal, the deprotonated hydroxamate group represents an intermediate between the keto/enol tautomers and forms a five-membered chelate ring with the thallium(I) cation. The coordination sphere of the cation is augmented to a distorted disphenoid by two monodentately binding O atoms from two adjacent anions, leading to the formation of zigzag chains extending parallel to the b axis. The cohesion within the chains is supported by π–π stacking [centroid–centroid distance = 3.746 (3) Å] and intermolecular N—H...N hydrogen bonds.