Biobased and biodegradable polymers can form the basis of an environmentally preferable, sustainable alternative to current materials based exclusively on petroleum feedstocks. Beyond this, biopolymers are generally capable of being disposed in safe and ecologically sound ways through disposal processes (waste management). Due to it, these materials have attracted great interest from both academic research and industrial manufacturing. In recent years, extensive studies have been conducted on the study of the poly(lactic acid) (PLA) properties, because of its being a typical biobased and biodegradable polymer, with good mechanical properties. However, its toughness and gas barrier properties are not satisfactory. The literature reveals that if a good dispersion is achieved, rigid particle toughening will be more beneficial than rubber toughening since both stiffness and toughness can be increased. Beyond this, a good dispersion of the filler in the PLA matrix should also improve the barrier properties. In the present work, composites based on PLA/CaCO3 nanoparticle were prepared in a Teck Tril twin screw extruder with L/D=36 and D=20 mm. Natureworks PLA was used and the nano-sized calcium carbonate (NPCC201), n-CaCO3, was supplied by Lagos Company. The grade of n-CaCO3 was coated with stearic acid for better dispersion and its particles are with an average particle size of 40 nm. A factorial experimental design was used to investigate the influence of the independent variables (n-CaCO3 and screw speed) on the properties of the materials. An intermediate level to each factor was also used. The dependent variables analyzed were Young’s modulus, Melt Flow Index (MFI), impact strength and the zero shear viscosity. Previous results showed that the addition of the nanofiller increased the resistance to crack propagation while maintaining the rigidity of the PLA matrix. An increase in the zero shear viscosity was also achieved when nanofiller was added.