Oleic acid-grafted chitosan oligosaccharide (OA-g-CSO) was synthesized to prepare self-assembled nanoparticles by sonication at physiological pH value (7.4). The nanoparticles appeared to be spherical in shape with a diameter of 158.1 ± 64.3 nm. The biocompatibility of OA-g-CSO nanoparticles was evaluated in vitro via MTT assay and hemolysis test. The nanoparticles showed no cytotoxicity to mouse embryo fibroblasts and the hemolysis rates came well within permissible limits (<2 %) in the tested conditions. When incubated with bovine calf serum, the protein adsorption on the surface of OA-g-CSO nanoparticles was concentration-dependent, and the amount of bovine serum albumin was in the highest proportion of the total amount of adsorbed proteins. Cellular uptake rate was evaluated by incubating fluorescence labeled OA-g-CSO nanoparticles with human lung carcinoma cells (A549). OA-g-CSO nanoparticles could be taken up by A549 cells, and the uptake rates increased with incubation time and particle concentration.