The aim of this work was to study the effect of the innovative combination of microcrystalline cellulose (MCC) and silver nanoparticles (Ag) on the poly (lactide acid) (PLA) composite properties, to modulate the PLA mechanical response and induce an antibacterial effect. The preparation and characterization of PLA-based composites with MCC and Ag nanoparticles by twin-screw extrusion followed by injection molding is reported. A film procedure was also performed to obtain PLA and PLA composite films with a thickness ranged between 20 and 60 mu m. The analysis of disintegrability in composting conditions by means of visual, morphological, thermal, and chemical investigations was done to gain insights into the post-use degradation processes. Tensile test demonstrated the MCC reinforcing effect, while a bactericidal activity of silver-based composites against a Gram-negative bacteria (Escherichia coli) and a Gram-positive bacteria (Staphylococcus aureus) was detected at any time points and temperatures analyzed. Moreover, the disintegrability in composting showed that MCC is able to promote the degradation process. The combination of MCC and Ag nanoparticles in PLA polymer matrix offers promising perspectives to realize multifunctional ternary composites with good mechanical response and antibacterial effect, maintaining the optical transparency and the disintegrability, hence suitable for packaging applications. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012