Starch as an inexpensive and renewable source has been used as a filler for environmental friendly plastics for about two decades. In this study, glycerol was used as a plasticizer for starch to enhance the dispersion and the interfacial affinity in thermoplastic starch (TPS)/polybutene-1(PB-1) blend. PB-1 was melt blended with TPS using a single screw extrusion process and molded using injection molding process to investigate the rheological and mechanical properties of these blends. Rheological properties were studied using a capillary rheometer, and the Bagley's correction was performed. Mechanical analysis (stressstrain curves) was performed using Testometric M350-10 kN. The rheological properties showed that the melt viscosity of the blend is less than that of PB-1, and the flow activation energy at a constant shear stress of the blend increases with increasing glycerol content in the blend. The mechanical experiments showed that both stress and strain at break of the blends are less than that of PB-1, whereas the Young's modulus of the most blends is higher than that of PB-1 which confirms the filling role of TPS in the blend. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012