The influence of the chemical composition on the phase structure, and from this the structure-property relationships, of poly[ester-block-ether] (PEE) elastomers based on poly(butylene terephthalate) (PBT) hard segments and oligo(α,ω-dihydroxy poly(oxytetraniethylene)) (PTMO) and/or dimer fatty acid (DFA) soft segments was investigated using differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and tensile testing. Differences in thermal and mechanical properties with varying hard and soft segment composition are interpreted in terms of the phase miscibility of the various polymers studied.