The branched thermoplastic polyether-ester elastomer (TPEE) and diisocyanate compound was melt extruded in an effort to enhance melt viscosity for the blow moulding process. The chain-extended TPEE was prepared with melt condensation of a branched TPEE and 4,4'-diphenylmethane diisocyanate (MDI) for enhancement of the molecular weight of TPEE. The effects of MDI contents as a chain extender on melt, thermal, mechanical and rheological properties of the chain-extended TPEE were investigated. By using a solution and melt viscosity analysis, the chain-extended TPEE was found to be an enhancement of molecular weight and a lightly cross-linked structure. The intrinsic viscosity (IV) increased and melt flow index (MI) decreased with an increasing amount of MDI due to the reaction between the hydroxyl end groups of TPEE and isocyanate groups of MDI. The chain-extended TPEE does not lead to an important drop in elongation at break. The tensile strength and the tear strength are characterized by a significant increase, compared with a branched TPEE. The storage modulus, loss modulus and the complex viscosity of the chain-extended TPEE were also higher. The modified Cole-Cole plots revealed that the chain-extended TPEE shows a higher elasticity than the branched TPEE. The chain-extended TPEE has more suitable melt and rheological properties for the blow moulding processes.