In this work, relationship between morphology and rheological properties of low-density polyethylene / linear low-density polyethylene / thermoplastic starch (LDPE/LLDPE/TPS) blends with the aim of controlling the rheological properties and morphology improvement is studied both experimentally and theoretically. Such relationship paves the way to develop packaging film with desired physical and mechanical performance. Considering the effects of starch modification, the change of processing method to modify starch and nanoclay addition; on the morphology and rheological properties of the blends, four different blends based on LDPE/LLDPE (70/30) (which is common in film packaging applications) containing various amounts of TPS, in the presence of maleic anhydride grafted polyethylene (PE-g-MA) as a compatibilizer are prepared in a twin screw extruder and then converted to the appropriate thin films using a film blowing machine. The morphological studies indicate that in the blends containing 5-20 wt. % TPS (prepared with addition of 35 wt. % glycerol in an internal mixer, TPS1), there is a relative good dispersion of starch particles in LDPE/LLDPE matrix which is attributed to the chemical interactions between MA groups in PE-g-MA and hydroxyl groups of TPS1. However, as the TPS1 content increases, the starch particle size increases too. On the basis of rheological analyses, high elastic nature of TPS1 and the large difference between viscosities of TPS1 and LDPE/LLDPE cause increasing the starch particle sizes. This results in increasing the stress concentration sites and consequently decreasing the tensile strength of the final films, as TPS1 content increases. Considering the viscosity and elasticity ratios of dispersed phase to matrix as the effective factors on the controlling rheological properties and morphology improvement and in order to suppress coalescence of starch particles in PE matrices, the effect of thermoplastic oxidized starch (TPS2, with higher fluidity and lower viscosity) and containing the same amount of glycerol is evaluated. According to the results, despite the lower viscosity and elasticity ratios due to weakening interfacial interactions, morphology improvement and achieving the blends with better physical and mechanical performances is unsuccessful. In this study, using the twin screw extruder to prepare thermoplastic starch (TPS3, with similar amount of glycerol) leads to desired viscosity and elasticity ratios in the respective blends. As a result, significant decreasing in starch particle sizes with increasing the TPS3 content and also elongated shapes in higher TPS3 content (40 wt. %) are observed. In addition, the results show that simultaneous addition of PE-g-MA and 5 wt. % nanoclay with partial exfoliated structure is one of the effective approaches to improve the morphology of LDPE/LLDPE/TPS blend and produce the material with superior physical and mechanical properties. In this work, emulsion rheological models explain the relationship between morphology and rheological properties of the LDPE/LLDPE/TPS blends well.