The target of this research is to study the toxic effect of silver nanoparticles (AgNPs) on seed germination and seedling growth of faba bean (Vicia faba L.). Seeds of V. faba were soaked in 50, 100, 200 and 400 mg/L of chemically synthesized AgNPs for 24 h. The shoot length was significantly reduced upon exposure to 200 mg/L of AgNPs compared to the control. There was no significant difference in root elongation, although the number of lateral roots decreased significantly at 200 and 400 mg/L compared to the control. Seedling vigor index decreased only at 200 mg/L. Conclusively, AgNPs were toxic to seedling development of V. faba at high concentrations. This study also showed that the number of lateral roots is a useful index to evaluate the effect of nanomaterials on early seedling growth.