The crystal structures of sodium 4-([4-[N,N-bis(2-hydroxyethyl)amino]phenyl]diazenyl)benzoate 3.5-hydrate, Na+*C17H18N3O4-*3.5H2O, (I), and potassium 4-([4-[N,N-bis(2-hydroxyethyl)amino]phenyl]diazenyl)benzoate dihydrate, K+*C17H18N3O4-*2H2O, (II), are described. The results indicate an octahedral coordination around sodium in (I) and a trigonal prismatic coordination around potassium in (II). In both cases, coordination around the metal cation is achieved through O atoms of the water molecules and hydroxy groups of the chromophore. The organic conjugated part of the chromophore is approximately planar in (I), while a dihedral angle of 30.7 (2) degrees between the planes of the phenyl rings is observed in (II).