The asymmetric unit of the title compound, C5H11NO2S·C5H12NO2S+·C6H2N3O7−, is composed of two crystallographically independent methio­nine residues and a picrate anion. The methio­nine and protonated methio­ninium residues are bonded through a strong O—H⋯O hydrogen bond, and an inversion-related dl1 head-to-tail sequence along the a axis is observed in the zwitterion. The amino groups of two residues connect to the lone oxygen of two inversion-related picrate anions. Hydro­phobic layers are observed in the y = 0 plane.