In this work, we have prepared thermoplastic starch (TPS) / polylactic acid (PLA) blends, and investigated the rheological properties as well as morphology of the blends. Thermoplastic starch, prepared using a combination of sorbitol and glycerol plasticizers, was melt blended with PLA in the concentration range of 20 to 80 wt.% in a laboratory twin screw extruder. Compatibilized blends were also obtained with substitution of 20 wt.% of PLA by maleic anhydride grafted PLA (PLA-g-MA). Scanning electron microscopy (SEM) images revealed co-continuous morphology in blends containing 40 and 60 wt.% PLA, while in blends with 20 and 80 wt.% of PLA, matrix-dispersed morphology was observed. Incorporation of compatibilizer resulted in formation of finer morphology in the entire blends. Moreover, in the presence of the compatibilizer, morphology of the blend containing 60 wt.% turned to matrix-dispersed. Rheological evaluations illustrated reduction of complex viscosity by introduction of compatibilizer. It was observed that the rheological properties of compatibilized blends were lower than those of their non-compatibilized counterparts. This observation was attributed to the chain session of PLA during maleic anhydride grafting reaction as evidenced by lower complex viscosity of PLA-g-MA compared to the neat PLA. In addition, it was found that in the samples with co-continues morphology, rheological properties are strongly dominated by the TPS phase. Moreover, in the blend samples containing 80 wt.% PLA, the rheological properties are negatively deviated from mixing rule; probably due to migration of glycerol and sorbitol plasticizers into the PLA matrix.