In this study, poly(lactic acid) was melt blended with high density polyethylene to investigate the rheological and mechanical properties of these blends. The rheological properties were characterized where viscous properties were evaluated in the molten state. In studying the viscous properties, non-Newtonian index (n), apparent viscosity, and the flow activation energy were determined. Mechanical properties were studied in terms of tensile properties, i.e. ultimate tensile strength, Young's modulus, elongation, and total energy at fracture. The results showed that PLA/HDPE blends and their pure components behave pseudoplastically (n