Since the approval by the Food and Drug Administration (FDA), ferumoxytol and other iron oxide nanoparticles (IONs) have been widely used as iron supplements for patients with iron deficiency. Meanwhile, IONs have also been used as contrast agents in magnetic resonance imaging and as drug carriers. Importantly, IONs have demonstrated a significant inhibitory effect on the growth of tumors, including hematopoietic and lymphoid tumors, such as leukemia. In this study, we further demonstrated the effect of IONs on inhibiting the growth of diffuse large B-cell lymphoma (DLBCL) cells by enhancing ferroptosis-mediated cell death. IONs treatment caused an accumulation of intracellular ferrous iron and the onset of lipid peroxidation in DLBCL cells as well as the suppressed expression of anti-ferroptosis protein Glutathione Peroxidase 4 (GPX4), thereby leading to increased ferroptosis. Mechanistically, IONs increased cellular lipid peroxidation through the generation of ROS via the Fenton reaction and regulating the iron metabolism-related proteins, such as ferroportin (FPN) and transferrin receptor (TFR), which elevated the intracellular labile iron pool (LIP). Hence, our findings suggest the potential therapeutic effect of IONs on the treatment of patients with DLBCL.