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 group-modified ethylene-octene based copolymer resin, as a chain extension/hydrolysis resistance agent for blow 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 properties, melt viscosity and parison stability, and in particular, exhibits superior blow molding, contains no gel, reduces production of odor-causing substances such as volatile organic compounds (TVOC) during blow molding, and maintains a balance between physical properties, moldability and operation environments.