In this study, thermoplastic starch (TPS) was mixed with low density polyethylene with different melt flow indexes in a one-step extrusion process to produce LDPE/TPS blends varied from 32% to 62% by weight of TPS. The influence of starch content and LDPE viscosity on morphology, biodegradation and tensile properties of LDPE/TPS blends were evaluated. Starch continuity and biodegradability were studied by hydrolytic, enzymatic and bacterial degradation. The LDPE viscosity had a considerable effect on the morphology and the connectivity of the starch particles. Evaluation of hydrolytic extraction showed that blends having TPS content above 50 wt% possessed a full connectivity. Studies of biodegradation indicated that the bacterial attack on starch resulted in weight loss of TPS of 92%, 39% and 22%, for PE1/TPS having 62% and 32% TPS, and PE2/TPS (31% TPS), respectively. Comparatively, the weight loss was more significant at 100%, 66% and 31% by hydrolytic extraction. Differences between these two techniques were discussed in terms of the accessibility of starch domains to microorganisms. Tensile properties (epsilon(b) and E) decreased with increasing exposure time to activated sludge. Changes in tensile properties were highly dependent on the biodegradation rate. PE1/TPS blends having 32% starch remained ductile after 45 days of exposure to bacterial attack.