Bacteriolytic therapy with Clostridium novyi-NT has shown promise as a form of cancer treatment, but concerns remain regarding route of delivery and toxicity. Our study aimed to develop a method to visualize delivery with MRI during bacteriolytic therapy. We did so by incubating bacteria with iron oxide particles. In vitro viability studies and labeling efficiency studies were then performed, followed by phantom studies. Bacteria were then directly injected into rat liver tumors as well as mouse flank tumors and imaged. We demonstrate that the labeled bacteria can be directly visualized on MRI and is a reliable indicator of successful delivery.