Inflammatory myofibroblastic tumor (IMT), a rare sarcoma, is primarily treated via resection of the mass. However, there is no standard treatment for recurrence or unresectable tumors. Almost 50% of IMTs carry ALK gene rearrangement that can be treated using ALK inhibitors, but therapeutic options for ALK-negative tumors are limited. This report describes a woman aged 22 years with unresectable ALK-negative IMT. Next-generation sequencing revealed a TFG-ROS1 fusion, and she had a partial response to the ROS1 inhibitor ceritinib. This report provides the first published demonstration of a patient with IMT with ROS1 fusion successfully treated using ceritinib. Our study suggests that targeting ROS1 fusions using the small molecule inhibitor shows promise as an effective therapy in patients with IMT carrying this genetic alteration, but this requires further investigation in large clinical trials.