The ethoxycarbonylcholine ion in the title compound (C8H18NO3+.C6H2N3O7-.0.5H(2)O) adopts a partly folded conformation with C-O-C-C and O-C-C-N torsion angles of +/-174.59(7) and -/+83.60(9)degrees, respectively. The carbonyl C atom has a partial positive charge, and electrostatic interactions are observed between this C atom and the nitro groups of the picrate ion. Interactions between the quaternary ammonium group and the O atoms of the ester group may be described as (CH... O) hydrogen bonds. Each phenolate O atom is involved in a hydrogen bond with a water molecule, forming a picrate-water-picrate linkage. The water molecule is situated on a twofold axis.