The modification of nanocrystalline cellulose with poly(L-lactic acid) was carried out using the "grafting from" approach based on the ring-opening polymerization of L-lactide initiated with cellulose hydroxyls. The modification was proved by FTIR spectroscopy, thermogravimetric analysis and dynamic light scattering. Samples of native and modified cellulose were applied as fillers for poly(ϵ-caprolactone) films that were studied for their mechanical properties. A significant increase of Young's modulus was observed for composite material based on PCL containing nanocrystalline cellulose modified with poly(L-lactic acid).