Biodegradable nanocomposites were prepared from polyvinyl alcohol (PVA) and cellulose nanofiber (CNF) by using liquid nitrogen, freeze drying and hot press techniques. The effect of CNF content on the biodegradability of the films was investigated by visual observation, scanning electron microscopy (SEM), weight loss, CO₂ evolution, differential scanning calorimetry, measuring the amount of mineralized carbon of the specimens buried in municipal solid waste. Ecotoxicity was evaluated by plants growth tests with cress and spinach. The results confirmed that the weight loss of nanocomposites was lower than that of neat PVA because of the zigzag pathways of microorganisms in the CNF presence. The SEM analysis showed extensive surface roughness and cracks for all samples, indicating the initiation of biodegradation. The CO₂ evolution decreased with increasing CNF content from 0% to 10% and then, increased with further increase in the filler content (up to 30 wt%). The crystallinity of the PVA and its nanocomposites increased as a function of time because of the amorphous parts degradation. Preliminary results of the ecotoxicological test revealed that all the nanocomposites and neat PVA did not generate any negative effects on germination or development of the studied vegetal species.