In this study, two novel, bio-based, amorphous polyester diols, namely poly(1,2-dimethylethylene adipate) (PDMEA) and poly(1,2-dimethylethylene succinate) (PDMES) are used to prepare thermoplastic poly(urethane urea)s (TPUUs). Interestingly, the TPUUs based on PDMEA show similar thermal and mechanical properties as their counterparts based on poly(1,2-propylene glycol). By decreasing the hard segment length, the flow temperature (Tfl) of the TPUUs decreases. The Tfl values of the 3U series are around 170 °C, which is below their degradation temperatures. The methyl groups adjacent to the ester groups in PDMEA and PDMES may hinder the hydrolysis of the polyester soft segments in the TPUUs.