A powerful methodology for the synthesis of unsaturated polyphosphoesters (UPPEs) relying on acyclic diene metathesis (ADMET) polymerization is described. A facile two-step protocol gives fast access to structurally versatile and potentially degradable and biocompatible materials. For the first time this allows to control the microstructure of either backbone and/or side chains of polyphosphoesters. Four different monomers are polymerized under different conditions to yield UPPEs with molecular weights ranging from 7000 up to 50 000 g mol–1 with reasonable polydispersity. The unsaturated and saturated polyphosphoesters are characterized in detail with various techniques. A major benefit of the UPPEs is revealed by differential scanning calorimetry proving the control over thermal properties with tunable melting or glass transition temperatures for the different saturated and unsaturated PPEs which is an important feature for future applications. This unique combination of the benefits of metathesis polymerization and phosphorus chemistry is a highly versatile system for materials in many applications ranging from adhesives to biomaterials.