Bismuth (Bi) is a minor metal used in semiconductors as a lead substitute. We have previously demonstrated that Bi inhibits plant growth and causes cell death. However, the mechanism of growth inhibition by Bi remains unclear. Reactive Oxygen Species (ROS) are involved in the phytotoxicity of heavy metals. The effect of Bi on ROS production in plants is unknown. We examined O₂ ^.− and H₂O₂ involvement in Bi-treated Arabidopsis thaliana and found that these have decreased production in Bi- treated leaves and roots. SOD is involved in ROS metabolism, and the FeSOD expression level was not affected upon Bi treatment. In Bi-treated root meristems, the cell cycle was arrested. However, the genomic DNA of Bi-treated plants was not digested. Therefore, Bi may inhibit enzymes related to the cell cycle. These findings indicate that Bi phytotoxicity causes ROS disruption and cell cycle arrest.