A new aqua-soluble Cu II -Na coordination polymer, {[Cu(H 2 O)Na(H 2 O)( η 9 -L)]·2H 2 O} n , was easily generated by self-assembly from copper(II) nitrate, sodium hydroxide and 2-hydroxy-5-nitro-3-(2-(2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene)hydrazinyl)benzene sulfonic acid (H 3 L) a new hydrosoluble arylhydrazone of barbituric acid. The complex was characterized by IR spectroscopy, elemental and single‐crystal X-ray diffraction analyses, which disclosed 1D metal-organic chains driven by the intricate nona-chelation of the fully deprotonated L 3− derivative to five metal cations (three Na I and two Cu II ). These chains have intercalated crystallization water molecules enabling the expansion of the structure to 3D by means of extensive hydrogen bond interactions. A new aqua-soluble Cu II -Na 1D coordination polymer with intercalated crystallization water molecules has been synthesized by using arylhydrazone of barbituric acid as a nonadentate versatile ligand. ► A new type of aqua-soluble copper(II)-sodium heterometallic coordination polymer has been prepared and fully characterized. ► Previously unknown arylhydrazone of barbituric acid was used for the first time as a nonadentate versatile ligand. ► Intercalated water clusters support the overall 3D supramolecular arrangement.