Lab-scale bead foaming reactor was used to investigate the foaming behavior of thermoplastic polyurethane (TPU) samples with different hard segment contents of around 39 %, 49 % and 57% and similar molecular weights and chemical composition. The saturation temperature, pressure, and time differently influenced the formation of hard segments with different close-packed structures and sizes. Consequently, with the increase in hard segment content during the saturation the heterogeneous cell nucleation was improved and the foam expansion was controlled by the stiffness of the TPU/CO2 mixture and solubility of CO2. As the saturation temperature increased the expansion ratio tended to increase while the cell density decreased due to the reduced hard segment crystallites generated during the saturation. Increase in pressure also improved the CO2 solubility more effectively and hence the expansion ratio was increased more significantly. The saturation time also influenced the amount and perfection degree of hard segment crystals. The interrelation between the crystallization behavior of the TPU bead foams and process conditions was reported using DSC and SEM analysis.