In the title hydrated mol-ecular salt, C(18)H(23)N(2) (+)·C(6)H(4)ClO(3)S(-)·H(2)O, which shows moderate biological activity against methicillin-resistant Staphylococcus aureus (MRSA), one ethyl group of the 2-[4-(diethyl-amino)-styr-yl]-1-methyl-pyridinium cation is disordered over two orientations in a 0.604 (13):0.396 (13) ratio. The main part of the cation is nearly planar with a dihedral angle of 4.50 (10)° between the pyridinium and benzene rings. In the crystal, the components are linked by O-H⋯O hydrogen bonds and C-H⋯O weak inter-actions. Aromatic π-π stacking inter-actions with centroid-centroid separations of 3.7363 (12) and 3.7490 (13) Å also occur.