Disclosed are a thermoplastic polyester elastomer resin composition and a molded article comprising the same. More specifically, disclosed is a thermoplastic polyester elastomer resin composition which comprises a glycidyl-modified ethylene-octene copolymer resin, as a chain extension/hydrolysis resistance agent for blown and extrusion molding to improve melt viscosity, and increases a molecular weight through reaction extrusion and thus exhibits superior heat resistance, weather resistance, heat aging resistance, hydrolysis resistance, fatigue resistance, melt viscosity and parison stability, and in particular, exhibits superior blow molding, causes no gelation, and reduces production of odor-causing substances such as volatile organic compounds (TVOC) during blow molding, thereby making a balance between physical properties, molding property and operation environments.