A new crystal of 2-amino-3-methylpyridinium dihydrogenomonoarsenate has been prepared and characterized by X-ray crystallography, thermal analysis and spectroscopic studies. This compound crystallizes in the triclinic space group P1¯ with a=7.2689 (2)Å, b=8.0975 (2)Å, c=8.3969 (4)Å, α=77.09 (3)°, β=79.20 (3)°, γ=88.16 (2)°, V=473.19 (3)Å 3 , Z=2. The crystal structure was solved and refined to R=0.027 with 3375 independent reflections. The atomic arrangement can be described as (H 2 AsO 4 − ) n polymeric chains anchoring the 2-amino-3-methylpyridinium cations through short hydrogen bonds. All the ring atoms of the organic entity are coplanar. The exocyclic N atom is an electron receiving center, which is consistent with features of imino resonance evidenced by bond lengths and angles. Solid-state 13 C and 15 N CP-MAS-NMR spectroscopies are in agreement with the X-ray structure. Ab initio calculations allow the attribution of carbons and nitrogen to the independent crystallographic sites.