This study investigated the effect of two different concentrations (0.05% and 0.1%) of chitosan nano-particles (CsNPs) as priming solutions (for 6 h) of Vicia faba seeds cv. Sakha 1, followed by germination and subsequent growth of seedlings for seven days. Chitosan nanoparticles were prepared using methacrylic acid and showed a mean size of 20 ± 2 nm. Both concentrations of chitosan nanoparticles caused deleterious effects on germination and seedling growth criteria. Germination was greatly reduced in both concentrations as compared to control (distilled water). The magnitude of decrease was much pronounced with the higher concentration of chitosan nanoparticles (0.1%). On the other hand, the lower concentration of CsNPs (0.05%) increased the content of total phenols and the activities of antioxidant enzymes (catalase, ascorbate peroxidase, peroxidase and polyphenol oxidase) as compared with those of the control seedlings. This might indicate that the relatively low concentration of chitosan nanoparticles enhanced the defense system of seeds by increasing total phenols and antioxidant enzyme activities.