A series of metallopolymers were prepared from cobalt(II) ions as chloride and a polyesterurethane having different molar ratios metal ions/urethane groups. The microstructure and macroscopic properties of the metallopolymer films (CoPU) were investigated in comparison with those of the parent polymer film (PU) by various techniques: atomic absorption spectrometry (AAS), ultraviolet and visible (UV–vis) absorption spectroscopy, Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA) and tensile testing. Cobalt(II) ions predominantly form tetrahedral coordination complexes with the nitrogen atoms in the hard segments, the intermolecular complexation bringing about coordination crosslinking. Complexation causes the disturbance of the initial interurethane hydrogen bonding and induces changes in the crystallinity of the hard-segment domains. The mechanical and viscoelastic behaviours of CoPU result from an intricate interplay between several phenomena occurring within the polymer matrix (such as complexation, hydrogen bonding and crystallization). For CoPU compared with PU, the initial thermal stability is diminished and the main steps of the thermal decomposition process are favoured.