The biocompositefilms were prepared from poly(L-lactic acid) and cel-lulose nanocrystals. To improve interfacial compatibility of hydrophilic cellulosenanocrystals with hydrophobic matrix polymer as well as to provide the osteocon-ductive properties, cellulose was functionalized with poly(glutamic acid). Themodified cellulose nanocrystals were better distributed and less aggregated withinthe matrix, which was testified by scanning electron, optical and polarized lightmicroscopy. According to mechanical tests, compositesfilled with nanocrystalsmodified with PGlu demonstrated higher values of Young’s modulus, elongationat break and tensile strength. Incubation of composite materials in model buffersolutions for 30 weeks followed with staining of Ca2+deposits with AlizarinRed S assay testified better mineralization of materials containing PGlu-modifiedcellulose nanocrystals asfiller. As the result of in vivo experiment, the developedcomposite materials showed less level of inflammation in comparison with purepolymer matrix and compositesfilled with non-functionalized cellulosenanocrystals.Keywords:Bio