Sydnones, which contain a mesoionic five-membered heterocyclic ring, are more stable if synthesized with an aromatic substutuent at the N3 position. In the title compound {sys-tematic name: 4-acetyl-3-[2-(eth-oxy-carbon-yl)phen-yl]-1,2,3-oxa-diazol-3-ylium-5-olate}, C13H12N2O5, the aromatic substitutent is 2-(eth-oxy-carbon-yl)phenyl. Intra- and inter-molecular hydrogen bonds are observed. The inter-planar angle between the sydnone and benzene rings is 71.94 (8)°. π-ring⋯carbon-yl inter-actions of 3.2038 (16) Å arise between the sydnone ring and a symmetry-related C=O group.