The purpose of this study was to investigate the effects of microcrystalline cellulose (MCC) content on the properties of polylactide (PLA) biocomposites; including the influences of maleic anhydride (MA) grafted PLA copolymer compatibilization. PLA/MCC biocomposites were produced by industrially compatible production techniques, i.e. twin-screw extrusion melt-mixing for compounding and injection molding for shaping of bulk specimens. SEM analysis and mechanical tests indicated that use of 3 wt% MCC resulted in very uniform distribution and consequently improved properties especially in terms of ductility and toughness. For instance, compared to neat PLA, the increases in the values of % strain at break and fracture toughness were 78 and 31 %, respectively. After MA compatibilization, these increases became as much as 82 and 55 %, respectively. Moreover, DSC and TGA indicated that use of MCC resulted in no significant changes in the transition temperatures and thermal degradation temperatures of PLA.