TPUs are multi-block copolymers comprised of alternating rigid and flexible chain segments known as hard segments (HS) and soft segments (SS), which are of interest due to the wide array of properties because of the morphology they adopt based on composition. This means TPUs are suitable for a wide range of applications, such as tubing, coatings, footwear, films, fibers, and automotive to name but a few. The goal of this study was to understand the relationship between hard segment content and rheological properties of thermoplastic polyurethanes (TPUs) at elevated temperatures. The changes in phase transition behavior and structure were investigated through varying hard-to-soft segment ratios of a model thermoplastic polyurethane (TPU) system. Dynamic rheological measurements showed a high temperature phase transition related directly to the hard segment content. Extensional viscosity also detected a relationship between the hard-segment content and the material’s strain-hardening behavior. Annealing the samples near the phase transition temperature caused an increase in moduli as well as an inversion in extensional behavior. Material structure pre- and post-annealing was studied by means of TEM, AFM, SAXS and WAXS and allowed a model for the structural developed under high-temperature annealing to be developed. Understanding the material property changes associated with changes in composition and annealing could provide a route to further tailor materials.