We present a new thermogelling poly(ether urethane) consisting of poly(ethylene-butylene) (PEB), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments. Their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 1.7 to 11.9 wt%. The composition and structural information of the copolymers were determined by GPC and ¹H NMR. The critical micellization concentration (CMC) and thermodynamic parameters for micelle formation of these copolymers were determined at different temperatures by the dye absorption method. It was found that the incorporation of small quantities of PEB led to a significant decrease in the CGC of the thermogelling copolymers. Rheological characterization of the thermogels provided insight into the mechanical properties of the gel. The non-toxicity of the copolymer towards L929 mouse fibroblast cells provides us with great optimism in utilizing this material for biological or medical-based applications.