The crystal structure of catena-poly[[[acetato(1,10-phenanthroline-kappa(2)N,N')copper(II)]-micro-dicyanamido-kappa(2)N(1):N(5)] trihydrate], [[Cu(C(2)H(3)O(2))(C(2)N(3))(C(12)H(8)N(2))].3H(2)O](n), consists of a zigzag chain formed by the polymer [Cu(CH(3)COO)(dca)(phen)](n) (phen is 1,10-phenanthroline and dca is dicyanamide), with three water molecules per repeat unit of the polymer. The Cu(II) atom has a slightly distorted square-pyramidal coordination environment consisting of two N atoms of the phen ligand, two nitrile N atoms of different dca ligands, one of them axial, and one O atom of the acetate anion. The compound forms a one-dimensional chain using dca as an end-to-end bridging ligand. Non-covalent interactions, pi-pi stacking and hydrogen bonding mediate the bundling of the polymer chains into a three-dimensional structure, with the water molecules playing an important role in the hydrogen bonding.